GB1602448A - Methods of controlling tape recorder operation and of reversing direction of tape motion - Google Patents

Description

(54) METHODS OF CONTROLLING TAPE RECORDER OPERATION AND OF REVERSING DIRECTION OF TAPE MOTION (71) We SANGAMO WESTON, INC., a corporation organized and existing under the laws of the State of Delaware, formerly of P.O. Box 3347, Eleventh and Converse, Springfield, Illinois 62714 U.S.A., and now of 180 Technology Drive, Norcross, Georgia 30092 U.S.A. do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to methods of operation of tape recorders in general; and more particularly though not exclusively, it relates to such methods in the context of apparatus of very high quality for recording and reproducing electronic signals on magnetic tape which is commonly referred to as a laboratory tape recorder. Apparatus of this type may be used in collecting data from various sources, for example, for subsequent analysis on a computer.

The past few years have seen a new generation of analog and digital data measuring and analyzing equipment with ever-increasing performance requirements for instrumentation grade laboratory tape recorders. Highly accurate A/D converters capable of generating data or rates of 80 x 106 bits per second are available. Data conditioners such as logarithmic compressors/expanders, high speed multiplexers, and multilevel amplitude and phase modulators are used in many systems. Sophisticated real time wave analyzers permit examination of data down to one half hertz band width and versatile computer programs allows detailed examination of data under different conditions.

In many instances, the data appears as short bursts of less than one minute duration but with a bandwidth of 4 MHz or higher. In other applications, the event may last many hours or days. In the former case, it is often necessary to expand a one second event over several minutes for proper analysis and in the latter case, economy may dictate that data gathered over several days be analyzed in a few hours. Often the analyzing is done at places other than where the event took place.

In many cases, there are two particular locations on the tape which are of interest to the operator concerning the data recorded. These are the Beginning of the Data (BOD) and End of Data (EOD) footage locations. Typically, the BOD and EOD locations are recorded either on a voice track on the same tape by an operator during recording, or noted in a written log by the operator. Upon occurrence of a specific event that is to be used as the reference, a notation of the footage indicator may be made or, in some systems, the operator may have the option of resetting the footage counter to zero. During playback or analysis, the operator may have to calculate the location of the reference event as well as other events located with respect to it.

Occasionally, the operator may wish to have the tape recorder perform a particular operation at the BOD and/or EOD locations. One well known example is commonly referred to as "shuttle". The tape is first moved forward at the desired speed reproducing the recorded signal until the EOD location is reached. Then, the tape is automatically returned in fast reverse to BOD.

As far as the tape transport is concerned, in a number of sophisticated applications it may often be the limiting factor in data analysis by reason of the introduction of errors in amplitude, time and other factors into the recorded data. There is need for improvement of performance features related to the tape transport, for example as regards the reduction of velocity errors (flutter) for significant improvements in time-base errors.

According to one aspect of this invention there is provided a method of controlling the operation of a tape recorder having first and second reels for storing tape, transducer means, and transport means for transporting tape from one of said reels in predetermined relation with said transducer means onto the other of said reels, said transport means comprising a capstan, capstan drive means for driving said capstan responsive to speed select signals and further responsive to a feedback signal representative of the speed of said capstan motor for generating a phase lock signal when the speed of the capstan corresponds to the speed setting determined by said speed select signals; first and second drums, said tape being trained about said drums in wrapping engagement; means for moving said drums between a read position in which the tape span supported between said drums is in operative relation with said transducer, an idle position in which said drums are disengaged from said capstan, and a transport position in which said drums are in driving engagement with said capstan and said tape span is not in operative relation with said transducer, said method comprising: storing first speed select signals representative of a tape speed selected by an operator; transmitting second speed select signals to said drive means for operating said capstan at a predetermined, programmed slow speed; detecting said phase lock signal when said capstan is operating at said programmed speed while said drums are in said idle position; generating a control signal to place said drums in driving engagement with said capstan; and then transmitting speed select signals representative of the speed selected by said operator to drive said capstan drive means at the selected speed.

According to another aspect of this invention there is provided a method of reversing the direction of tape motion in a tape recorder having first and second reels for storing tape, transducer means and transport means for transporting tape from one of said reels in predetermined relation with said transducer means onto the other of said reels, said transport means comprising a capstan, capstan drive means for driving said capstan responsive to speed select signals and further responsive to a feedback signal representative of the speed of said capstan motor for generating a phase lock signal when the speed of the capstan corresponds to the speed setting determined by said speed select signals; first and second drums, said tape being trained about said drums in wrapping engagement; means for moving said drums between a read position in which the tape span supported between said drums is in operative relation with said transducer, an idle position in which said drums are disengaged from said capstan, and a transport position in which said drums are in driving engagement with said capstan and said tape span is not in operative relation with said transducer, said method comprising: storing signals representative of the present speed and direction of tape motion; storing first speed select signals representative of a tape speed selected by an operator; transmitting second speed select signals to said drive means for operating said capstan at a predetermined, programmed slow speed in the present direction; detecting said phase lock signal when said capstan is operating at said programmed speed while said drums are in driving engagement with said capstan; then disengaging said drums from said capstan; then de-energizing said capstan drive means; then energizing said capstan drive means in the reverse direction; then transmitting said second speed select signals to said drive means for operating said capstan at said programmed speed in the reverse direction after said capstan has stopped; detecting said phase lock signal when said capstan is operating at said programmed speed in the reverse direction with said drums disengaged from said capstan; generating a control signal to place said drums in driving engagement with said capstan; delaying a preset time; and then transmitting speed select signals representative of the speed selected by said operator to drive said capstan drive means at the selected speed.

A tape recorder incorporating apparatus in accordance with this invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a functional block diagram of the overall system; Figure 2 is a perspective view of a tape transport unit, taken from the front and side; Figure 3 is a close-up fragmentary perspective view of the transport with the cover removed; Figure 4 is an elevational rear view of the transport mechanism; Figure 5 is a vertical cross-sectional view taken along the sight line 5-5 of Figure 4; Figure 6 is a diagramatic front view of the tape transport illustrating the positions of the control and slave drums in the read, idle and transport positions, relative to the transducer heads; Figure 7 is a diagramatic front view illustrating the relationship of the tape to the crown of a transducer head; Figure 8 is a fragmentary perspective view of a portion of the transport including upper and lower vacuum chambers, with the cover removed; Figure 9 is a front elevational view of the control panel for the transport of Figure 2; Figure 10 is a diagramatic view, partly in functional block form and partly in circuit schematic form, of the principle control elements of the tape transport system and the interface with the Central Processor Unit; Figure 11 is a logic schematic diagram of the interface from the Control Panel to the Central Processor Unit; and Figure 12 is a logic schematic diagram of the interface circuitry between the Central Processor Unit and the Control Panel.

INDEX Page No.

I. Overall System .. ......... ........... ...................... ........... ....... 12 II. Tape Transport Mechanism ........................................ 14 III. Control Panel .. ............. ............ ........ .. 24 IV. CPU/Tape Transport Interface .. ......... ............. .. 28 V. CPU/Control Panel Interface . ........ .. 35 VI. Operation of CPU/Control Panel Interface .. ........................ .......... 39 VII. Overall System Operation .. ......... ......... .................. 45 A. START UP B. SPEED SELECTION .. ....................................... .................. 47 C. FORWARD/REVERSE . .. 50 D. RECORD .. . ........................ ........ .. 52 E. FAST FORWARD/FAST REVERSE .. ......... .. 53 F. ENABLE MODES. ............ .. 55 F1. ENABLE SEARCH .. ....... .. 55 F2. ENABLE TAPE SYNC .. ... 55 F3. ENABLE BOT/EOT ..... ........ 56 F4. ENABLE SHUTTLE .. ........ ... 61 G. MISCELLANEOUS . ......... .. 62 G1. ADVANCE TO BEGINNING OF DATA (TO BOD). 62 G2. SRP, TUP . .......... 63 G3. FOOTAGE .. ......... .. 64 G4. CALIBRATION . ........ ... 65 I. Overall System Referring first to Figure 1, the circuitry enclosed within the dashed block generally designated 1 comprises a Central Processor Unit (CPU). The CPU includes a processor unit 2, a memory 3 and interface (I/O) circuits 4. The processor unit 2 may be a microprocessor printed circuit board having a microprocessor chip sold under the designation M6800 by Motorola, Inc., and it includes a crystal oscillator providing a clock source as well as buffer circuits. The memory 3 contains three chips of 1,000 bytes of programmable read only memory (ROM), at least one of which is erasable (Part No. 2708 of Intel Corporation), and 128 bytes of random access memory (RAM). CMOS circuitry is preferred for random access memory because of the very low current drain when not being accessed.

The CPU communicates with a tape transport 5 by means of buses 6A, 6B, 6C and 6D.

Bus 6A is a control bus comprising eight function-control lines. Bus 6B is a speed select bus comprising four lines of parallel data which determine the speed of the tape transport 5. Bus 6C is a monitor bus comprising seven function-monitor lines; and bus 6D is an interrupt bus comprising four interrupt lines from the transport to the CPU.

The system is controlled from a control panel 7 which communicates with the CPU by means of two buses designated 8A and 8B. As will be explained in more detail in connection with Figure 12, bus 8A is a control bus comprising seven lines (six data lines and one "data present" line) from the control panel to the I/O circuits; and bus 8B comprises eight lines (seven data lines and one strobe line) from the CPU to the control panel 7.

A remote control capability can be incorporated into the system by communicating the bus 8B to the remote location, and by introducing a separate bus, similar to bus 8a from the remote location to the interface circuits 4. Since the CPU has interrupt capability, a remote control interrupt would be required in the main line program, but the operation and functioning would be similar to that to be described for the Control Panel 7. A remote control unit could be enabled or disabled at the Control Panel 7, and a speaker and microphone could also be added for voice commentary, if desired.

II. Tape Transport Mechanism Referring to Figure 2 an upright cabinet 10 has a lower front panel 12 and hinged glass front panel door 14 covering the top supply reel 16 and bottom take-up reel 18 mounted on their respective spindles 20 and 22. The glass door 14 also covers the transport 26 (see Figure 3) located between the reels.

A control panel 28 includes individual control switches and push buttons 29 and 30.

These control and function switches will be described in more detail below. A display 31 is used to display information such as footage or stored commands to the operator.

In Figure 3 the transport system 26 includes a pair of guide rollers 32 and 34 spanning the side opening of an upper vacuum chamber (to be described) covered by the hinged side plate 36, the first drum 40, the drive capstan 42, the second drum 44 and the second pair of guide rollers 46 and 48 spanning the side opening of a lower vacuum chamber behind the hinged cover plate 36.

The path of the tape 50 is from the feed or supply reel 16 over the roller 32 into the upper vacuum chamber, from this chamber over the roller 34, then around the drums 40 and 44 in major wrapping engagement, over the roller 46, through the second vacuum chamber, over the roller 48 and thence to the take-up reel 18. Because of the relatively close spacing of the drums 40 and 44 with each other and the capstan 42 and the absence of idlers, the transport system is said to be a short-loop configuration. The vacuum chambers perform the functions of tape-guiding, adding tape tension, and providing an indicator in the event the tape becomes tight or loose exceeding certain limits, and serve as a tape storage element, thereby buffering the capstan block assembly 52 from the reels 16 and 18.

As will be described, the drums 40 and 44 are rotatably mounted on crank shafts suitably carried by precision bearings within the capstan and head mounting block 52 for transport of the tape 50 into operable contact with the transducer assembly 54 (the read/record or simply "read" position), the individual transducers 56 of which perform the necessary record and play functions, known in this art.

Referring to Figure 4, the block 52 has a central circular recess 64 (from which the capstan has been removed) intersected diametrically by a top circular recess 66 and a bottom circular recess 68. The centers of all three recesses lie on a vertical center line 70.

Referring to Figure 5 the drive capstan 42 extends from its supporting drive shaft 76 beyond the front surface of the block 52 to a position between the drums 40 and 44 so that its peripheral. or drive, puck surface 77 is substantially diametrically between and spaced from the peripheral friction drive surface 78 of the drums (shown in the idle position in Figure 5).

The puck 77 is preferably composed of a tough thermoset such as cast liquid polyurethane having high abrasion and impact resistance, and the capstan 42 may be titanium.

An opening 80 in the block 52 houses the shaft 76 which is rotatably carried by the bearing housing 81 and driven by a motor 82 having a tachometer 83 carried at the end. A fixed rotational center 90 of the drive shaft 76 for the capstan 42 is shown in both Figures 4 and 5.

Each of the drums 40 and 44 is mounted on an identical shaft 100, shown in cross section in Figure 5 for the drum 40. These shafts each have a fixed axial portion A and a pivoted or movable portion B. The axes of portions A and B are offset. The center lines of rotation of the respective A portions of the shafts are shown at 102 and 104 in Figures 4 and 5, and those of the B portions are shown at 106 and 108. The B portions pivot about the same axes as portions A, i.e., axes 102 and 104. The portions B are the rotational axes for drums 40 and 44.

Referring more specifically to Figure 5, and using the shaft 100 for the drum 40 to illustrate the manner in which these shafts are mounted, it is seen that the housing 52 defines an opening 110 for the pair of precision bearings 112, the inner races of which engage the raised machined and true surfaces 114 of the fixed axial portion A.

The drum 40 is carried on the crank portion (spindle 138, Figure 5) B of the shaft 100 by means of bearings 130 and 132. The bearing assembly is retained within the central bore 140 of the drum 40.

The outer surfaces of the drums also provide a tape-carrying surface having a plurality of close-spaced circumferential shallow grooves 152 which eliminate air-bearing of the tape to the drums during high speed operations. A middle circumferential section 151 without grooves divides the grooves into two groups so that a 1 inch tape will span all of the grooves in the two portions, but a 1/2 inch tape will span only the grooves of one portion with an outer edge of the tape running along the smooth section 151.

The other ends of the shafts 100 are reduced at 154 and contain a flat portion 156 for mounting control hubs 160 and 162. The blocks 160 and 162 hold driven gears 170 and 172 on the respective shafts 100 for limited rotation about the axes 102 and 104, respectively.

Each of the driven gears 170 and 172 has an associated drive gear 174 and 176 meshing therewith. Reversible DC torque drive motors (not shown) are coupled to the drive gears 174, 176.

The control hubs 160 and 162 are mounted off-center to their respective shaft ends 154 of the crank shafts 100 and have swing ends 190 and 192. The arc traversed by the gears 170, 172 is little more than 1800, and the drive gears 174 and 176 are not approached by the sides 194 and 196 of the top hub 160 or the flat sides 198 and 200 of the bottom hub 162 because of positive stops to be described.

The hubs 160, 162 carry protruding pins 204, 206 which extend outwardly in Figure 4.

A pair of steel return-springs 208 and 210 is provided in relation to the top control hub 160, extending at slight angles to each other for contacting the pin 204. As the gear 170 is rotated about 90" in either direction from its idle position shown in Figure 4, the pin deflects one of the springs 208 and 210 and stops when either surface 194 or 196 engages one of the contact stops 306.

The hub 162 also has a pair of return springs 214 and 216. As the hub 162 and the gear 172 are rotated, the springs 214 and 216 act as a cushion, and hub surfaces 198 and 200 contact their associated stop surfaces 306. The springs 208, 210, 214 and 216 return drums 40 and 44 to idle position when torque is removed.

Still referring to Figure 4, a pin or stake 220 is carried on the underside and near the upper periphery of the lower gear 172. The hub 162 has an opening 228 which receives a spring post 230 extending upwardly from the gear 172. A pair of compression springs 232 are seated on roll pins extending from either side of post 230 and secured by set screws 234 and 236 in hub 162 adjacent opening 228. The spring post member 230 is resiliently held by the springs 232 so that the connection between the driven gear 172 and hub 162 and its associated axle 154 is a resilient coupling. As will be apparent from subsequent description, this resilient coupling permits the limit positions of the control drum to be adjusted without affecting the actuation of limit switches 260 and 262. In addition, it ensures that hub 44 is being driven by capstan 42 when drum 40 is moved into engagement with the capstan.

A pair of normally open limit switches 260 and 262 are mounted with their actuators 264 and 266 adapted to be engaged by pivotal switch blocks 268 and 270. Switch arms 274 and 276 of these switch blocks are engageable by the pin 220. The switches 260 and 262 control the electrical power to the reversible drive motor for the gear 170 which is referred to as the "slave" gear. The switch 260 is actuated (closed) by the pin 220 rotated in the direction of arrow R (standing for "read" or "record") with its switch arm 274 thereby pivoting the switch block 268 into contact with the actuator 264.

The switch 262 is similarly actuated (closed) by the pin 220 as it swings in the direction of the arrow LT (standing for "lift tape" or transport).

Figures 4 and 5 show a first pair of adjusting screws 280 and 282 and a second pair of adjusting screws 286 and 288. The shank 300 of each adjusting screw is threaded into a boss 304. As the gears 170 and 172 oscillate through the cycles of record or play ("read") to the fast forward and reverse ("transport") positions, the stop elds 306 of the adjusting screws function as limit stops at each end of the swing arc. By adjusting the screws, the stop ends 306 can be finitely adjusted to limit the swing arc of the respective hubs and hence control the degree of compression of the drums into polyurethane puck surface 77. Thus, the distances between the axis 90 of the capstan 42 and the peripheries of the drums 40, 44 along respective radial lines joining the axis 90 with the axes 106, 108 of the drums can be made equal to thereby ensure constant tangential velocity of the drums (and constant tape speed) because the drums are surface-driven by the same element, namely, the capstan.

Since the hub 160 is affixed to the gear 170 and the drive 174 is in constant engagement when the stops 306 function to stop the hub 160 at the end of its swing, the motor drive stalls. For this purpose a slip clutch or stall motor is used (which latter limits stall torque in stalled condition).

The overall operation of these parts is as follows: Assume the gear 172 of the control drum is driven in the "read" direction (CCW, i.e., counterclockwise, in Figure 4) from idle position. The gear 172 rotates until the pin 206 contacts the spring 214 causing the spring to deflect. The gear 172 continues to rotate until pin 220 engages the switch arm 274 thereby rotating the block 268 toward the actuator 264 of the switch 260. The gear 172 continues to rotate causing hub 162 to contact the stop 306.

This limits rotation of the crank 100 and hence the control drum 44 since the hub 162, crank 100 and drum 44 are all rigidly connected.

At this point, the control drum 44 is in driven engagement with the puck 77. The gear 172 continues to rotate CCW (with the hub 162 against the stop end 306 of the screw 286) allowed by resilient coupling means, i.e., the springs 232, causing the spring 232 on that side to begin compressing. The gear 172 continues rotating until the switch block 268 contacts the activator 264 causing switch 260 to switch and the slave drum 40 to be driven to its "read" position. Adjustment of set screw 234 determines how much further gear 172 must rotate, after the hub 162 contacts the stop 306, to cause the switch 260 to be activated by the force of the block 268 against the activator 264.

Design requirements of resilient coupling between hub 162 and gear 172 are affected by the factor of switch 260 having to be activated after the hub 162 strikes against the stop 306.

This ensures that the control drum 44 is driving the tape 50 before the slave drum 40 engages the capstan, to maintain tension on the tape and to keep the tape in driving relationship with the capstan to prevent a drop, or fluctuation, in tape speed. The adjustable means, namely spring biased post 230, controls the point at which switch 260 is actuated after the hub 162 has stopped.

It is apparent that the foregoing factors, movements and adjustments apply in reverse order when the controls are moved to call for the drums to move to the idle position and then to the lift tape (LT) or transport position. As the torque on the gear 172 is released, the spring arm 214 causes the drum 44 to move to the idle position, the drive capstan keeps rotating, but the switch 260 opens and the drum 40 is returned to its idle position as the drum 44 stops rotating. Movement of the control drum to the lift tape (transport) position (CW in Figure 4) causes the switch 262 to be actuated after the hub 162 strikes against the stop end 306 of the screw 288, again assuring that the control drum 44 is driving the tape 50 before the slave drum 40 begins rotating.

The relative movement of the eccentric axis 108 of the lower drum 44 to each side of the center 104 or idle position, toward and away from the transducer head assembly 54 and the relative following movement of the eccentric axis 106 of the upper drum 40 to each side of its center 102, toward and away from the transducer head assembly 54, as well as the relationship of the record and play heads 56 to the tape 50, are shown diagrammatically in Figures 6 and 7. The tape 50 passes in a short loop from the roller 34 in major wrapping engagement over the drums 40 and 44, past the transducers, back to roller 46 in the record or play mode and in a slightly shorter loop during the transport mode, since the drums 40 and 44 are closer to the rollers 34 and 46.

It is to be observed that the pivot axes 106 and 108 move in a short arc of about 4"13' in relation to the center of rotation 90 of the capstan 42. Also, as shown in Figure 7, when the drums are in the read position, the tape 50 enters and leaves the crown 308 of each head 56 with a 2 1/2" wrap and the sections of tape 50, indicated at 309, travel in an essentially straight-line relationship on each side of the points of crown contact.

The reduction in flutter and skew, and the increase in fidelity is augmented by the close proximity of a pair of vacuum chambers 310, shown in Figure 8. These chambers are identical in construction. The hinged cover plate 36 has been removed to show their interiors through which the tape 50 passes in the loops 50a and 50b in the direction of the arrows 312.

A pair of slots 326 communicate the interiors of the chambers with a plenum 324 mounted on the back side of the vacuum chamber. The plenum has a nozzle 328 which connects to a common and essentially constant source of partial vacuum, generated by a multistage fan type pump.

The chamber houses a series of light sources 141 and 142 such as light-emitting diodes at their ends and a closely spaced group of light sources labelled 144, 145, 146, 147 (also light-emitting diodes) located intermediate the ends of the chambers 310. The tops for each chamber include photocells 148 and 149 opposite and responsive to the light sources 141 and 142.

The top panels also house a series of inter-connected photocells behind appropriate glass panels, the series being indicated by the reference numerals 330. The photo-electric system just described is connected through suitable amplifiers to control the reel drive motors, as will be described.

The vacuum chambers each have an air flow distribution shoe 332 forming a partial closure and guide for the incoming and outgoing tape 50. These shoes have their top and bottom ends closely spaced from the top and bottom panels to provide a slit for entry and exit of the tape 50.

The shoes 332 define a series of uniformly sized and spaced air openings 334 which are open to the atmosphere on the side toward the rollers 32 and 34, and 46 and 48. At the top and bottom of each shoe a transverse roller 336 is provided to facilitate the passage of the tape therearound, especially under conditions of lessened tape tension. The portions of chambers 310 near the top and bottom of shoes 32 are covered with a tape 340, fastened by a pressure-sensitive adhesive, to provide a frictionless surface. The tape 340 is cut to form the grooves to augment the flow of air on the outside of the tape to form the loops 50a and 50b. Accordingly, the loops float or are cushioned by airflow on all sides.

The tensioning system works as follows: a partial vacuum is drawn at the ducts 326, through the plenum 324, and the reel motors begin to feed and take up the tape; air passes through the holes 334 and also through the grooves on each side of the tape at the ends of the shoes 332; the loops 50a and 50b gradually form, due to the in-rush of air; and the tape shuts out the passage of light from the source 141 to the photocell 148 as indicated by the normal operating position of the loop 50b in the lower chamber.

When the system is at the selected speed the ends of each loop will be opposite the light sources 144-147 and the photo detectors 330 will monitor this normal condition. If the loop in either chamber becomes too short, as indicated by the loop 50a in the top chamber, the photo system 144-147 and 330 will give a visual signal and proper adjustment of the speed of th switch 356A enables a reference timing signal previously recorded on the tape to control the speed of the capstan servo system (to be described) during the reproduce mode.

Fluctuations or perturbations of capstan motor speed may be reduced if a reference signal is recorded at the same time as data, and then used during playback. Any fluctuations in capstan speed during record will thus be reproduced accurately during playback, so the recorded signal appears to have been recorded at constant tape speed.

Most of the switches are of the momentary contact type. The only exceptions are the two rotary switches 363 and 365, the data entry switch 362 and the ENABLE switches 356A-D.

The four ENABLE switches operate as alternate action switches, that is, each successive pushing of the button toggles the memory location in the CPU assigned to that switch to its complementary state. If the ENABLE TS switch is off, the reference timing signal on the tape is not used.

The ENABLE EOT switch 356B is used to cause the system to execute User Commands at End of Tape (EOT) or Beginning of Tape (BOT) if such commands have been previously programmed or entered into the system, as will be described. The ENABLE SHTL (shuttle) switch 356C enables the programmable shuttle feature, to be described, the ENABLE SEARCH switch 356D allows the tape to remain against the transducer heads during a slew mode and changes the tape speed to 240 ips.

Beneath the ENABLE switches 356 is a power switch 357 which applies primary power to the system.

A READY switch 358 is used to command proper positioning and tensioning of the tape prior to initiation of any transport operation as discussed below in section VII A. It also operates as an alternate action switch.

Three indicators 359, 360 and 361 are used, respectively, to indicate that the capstan speed has reached the speed set by the switches 350, that the capstan speed is synchronous with the speed of a reference signal recorded on the tape (actuated by the ENABLE TS switch 356A), or that an alarm condition exists.

Manually actuated data entry switch means 362 comprises five individually settable binary coded decimal switches mechanically indicating their position. It is used to load either data or command signals by the operator into a storage location determined by a function switch 363. The data entry switch 362 displays numerical data, but, as will be understood from subsequent description the numerical data may represent a number (data), such as footage, or it may represent a command code, depending upon the position of the function switch 363. For example, if the function switch 363 is in the BOD position, the contents of the data entry switches 362 stored in the CPU by the operator will be used to define the footage location for Beginning of Data. On the other hand, if the function switch 363 is at the UCBOD (indicating User's Command at Beginning of Data), the numerical information in the data entry switch 362 (lowest order digit only in this case) will be representative of a command which will be stored in the CPU by the operator and later executed by the system when the tape reaches the BOD position.

A display pushbutton 364A causes the contents of a storage location, as selected by the function switch 363, to be displayed in the numerical display 31 adjacent the control panel 28 of Figure 2.

A LOAD pushbutton 364C causes the contents of data entry switch 362 to be sent to storage locations determined by function switch 363. A FOOTAGE RESET pushbutton 364B causes the contents of the footage memory location to be set to zero regardless of the position of function switch 363.

Since the system has the capability of being remotely controlled, a rotary switch 365 is used to select whether the local control panel, a remote control unit, or both are being used to control the system. The control panel also includes a volume control 366 and a speaker 367 over which a voice track on the tape may be reproduced.

IV. CPU/Tape Transport Interface Referring now to Figure 10 various elements of the tape transport and vacuum systems are shown in diagrammatic form with reference numerals corresponding to the structural elements already disclosed. The tape 50 is shown as trained around the roller 32 into the upper vacuum chamber 310, around the roller 34, and in major wrapping engagement with drums 40, 44. The drums are shown in the two capstan-engaging positions. The tape span between the drums in the transport position is shown in solid line, and for the read position, it is shown in dashed line, being in operative relationship with the transducer 56. The upper drum 40 is positioned by means of a first reversible dc torque motor 370 (which is connected to the previously described crank shaft 100 for that drum); and the position of the control drum 44 is determined by a similar motor 371.

The positioning of the drums in the read or transport positions is determined by the signals DRCS or DRFS which are fed from the I/O circuits 4 (commonly referred to as peripheral interface adapters) of the CPU 1 along the previously described bus 6A. In Figure 11 these lines are designated respectively 6A2 and 6A3. The signal DRCS actuates the motor 371 to place the control drum 44 in the read position which, in turn, by means of the microswitch 260 described above, causes the motor 370 to place the slave drum 40 in the read position. Similarly, the signal DRFS fed along bus line 6A3 causes the drums to be placed in the transport position.

A signal RECD is transmitted from the CPU along a line 6A1 to energize a relay 373 which, through a first pair of normally open contacts 374, 375 couples input power to the record electronics 376, which may comprise conventional circuitry, and has its output coupled to the transducer 56. A third set of contacts 378 closes to supply a ground signal along a bus line 6C7 (corresponding to one line of the previously described bus 6C of Figure 1) back to the CPU. This monitor signal is designated REC, and, of course, indicates that power is being supplied to the record head drivers.

A signal REVR is sent from the CPU along a line 6A4 to energize the coil of a relay 380 when a reverse pushbutton is depressed on the control panel. The relay 380, through a first set of contacts 381 supplies a ground signal along line 6C5, which signal is designated REV, and is indicative of the transport's operating in the reverse mode. Second and third sets of contacts 382, 383 are actuated when the relay 380 is energized to reverse the polarity of a source of electrical power to a power amplifier 385 which is controlled by a capstan servo 386, and is used to drive the capstan motor 82, which is a high torque, low inertia DC motor having a speed responsive to the repetition rate of input pulses.

When the operator desires to set the speed of the tape, he presses one of the speed selection switches 350 (Figure 9), and the information is communicated to the CPU in a manner to be described. The CPU then sends a coded set of signals along the parallel 4-bit bus 6B to a decoder 400.

The signals fed along the speed select bus 6B are in hexadecimal code, only ten positions of which are used corresponding to the ten predetermined speeds at which an operator is capable of running the transport. The decoded output of decoder 400 is coupled to a Divide by N circuit 401, the input of which is received from a crystal oscillator 403 by means of a switch 404. The switch 404 is actuated by a signal OPRT fed from the CPU along line 6A6.

The reference input to capstan servo 386 is connected to the contact arm of relay 407. In the de-energized state of relay 407, its contact arm is connected to the output of divider 401 which divides the frequency of crystal oscillator 403 in accordance with the decoded output of decoder 400. Pickup 387 senses the speed of motor 82 in cooperation with tachometer 83 and supplies a speed feedback signal to capstan servo 386 over relay contacts 390. Capstan servo 386 compares the feedback signal from pickup 387 with the reference signal from divider 401 to control the speed of capstan motor 82 in a well known manner.

In order to attain the slew rate of 320 ips, which is beyond the capacity of the controls provided for divider 400 and divider 401, relay 407 is energized to connect its contact arm to the output of Divide by n divider 408. Since "n" is smaller than any "N" frequency, the reference frequency input to capstan servo 386 is the highest available with this circuitry and, consequently, the capstan motor will be driven to its highest speed which as mentioned above, has been selected at 320 ips for the slew mode. It will be apparent that another speed may be chosen as well depending on the design specifications provided by a particular user.

If the signal input from the tachometer pickup 387 (representative of actual capstan speed) is equal to the reference signal input (either from divider 401 or divider 408) a signal LOCK is sent to the CPU along line 6C6. This signal, when present, indicates that the capstan motor is operating in a phase locked condition.

The feedback input of the capstan servo 386, as already mentioned, is received from a pickup 387 associated with the tachometer 83 of the capstan motor, and it is coupled to the capstan servo through a set of normally closed relay contacts 390 which are controlled by a relay coil 391. When the relay 391 is energized, the contacts 390 open, and a contact 392 is connected to the feedback input of the capstan servo. The relay 391 also actuates a set of normally open contacts 393 to generate a signal along the line 6C4 to the CPU, which signal is designated TC and indicates that the speed of the capstan is being controlled by a reference signal on the tape, as distinguished from the feedback pulse from tachometer 83 via pickup 387.

In order to cause the transport to operate in this mode, a signal TSEN (for "Tape Sync Enable") is transmitted from the CPU along a line 6A5 to an input of an enable circuit 395.

A second input on the enable circuit 395 is received from a detector 396 which senses whether a reference signal is present on a line 397. The line 397 is fed by a reproduce amplifier 398 from the transducer 56 and is used to reproduce the reference signal from the tape, if it is present. The line 397 is also connected to the normally open contacts 392, and fed to the capstan servo 386 if the relay 391 is energized. Thus, the relay 391 is energized in response to the command signal TSEN, but only if the reproduce amplifier 398 generates a reference signal, as detected by the detector 396.

The signal from the tachometer pickup 387 sensing speed of the capstan motor 82 is also coupled directly to a detector circuit 410 and a Divide by 200 circuit 411. The detector circuit 410 senses pulses from the pickup 387 and generates a level signal designated CMOT along line 6C2 (one line of the monitor bus 6C of Figure 1) to the CPU. This signal indicates that the capstan is in motion.

The divider circuit 411 generates a pulse for each 1/100 foot of tape travel for a purpose to be discussed below. These pulses are sent to the CPU as interrupt signals designated CAP along a line designated 6D1, forming part of the previously described Interrupt Bus 6D of Figure 1.

Turning now to the reel drive systems, a signal TENT is transmitted from the CPU along a line 6A8 to a position servomechanism 415 which receives a bias input 416 and also receives an analog signal from the solar cell photodetector 330 in the lower vacuum chamber (indicated by "C" for drawing clarity rather than by lines). The signal TENT provides an enable signal for the position servomechanism 415 to drive a motor 418, the output shaft of which drives the takeup reel 18.

A tachometer 419 generates pulses representative of the angular velocity of the takeup reel 18 and these pulses, coupled through a Divide by 60 circuit 420 provide interrupt pulses designated TUP to the CPU along the Interrupt Bus line 6D3 for a purpose to be discussed below. A similar closed loop servomechanism drive is provided for the supply reel 16, by means of a separate drive motor 421. A tachometer 422 sensing angular velocity of the supply reel 16 generates a train of output pulses which are coupled through a Divide by 60 circuit 425 to provide an interrupt signal SRP to the CPU along Interrupt Bus line 6D2. The signal TENT, together with the output signal of the supply reel tachometer 422 are coupled to an enable circuit 426, the output of which is used to activate the reel servomechanisms and the vacuum system, as functionally indicated in block 427.

The interrupt signals TUP and SRP contain a pulse for each revolution of the associated reel (takeup or supply). These signals are used, in a manner to be described, for determining the End of Tape positions by comparing them, in the CPU with the pulses CAP on line 6D1 which are representative of capstan angular velocity. As will be described, by comparing these pulses, a ratio can be obtained which is independent of operating speed but which is a true indicator of the diameter of the tape pack remaining on the respective reel. This method permits the operator to change the EOT position through a simple setting of the data entry switches 362, in combination with the function switch 363 and load push-button 364C, and without having to make any mechanical setting or adjustment.

The output signals of the individual photodetectors 148, 149 for both the upper and lower vacuum chambers are coupled to a logic circuit 430 which generates an output signal TT fed to the CPU along status bus line 6C1 when both tape loops within the respective vacuum chambers are within the prescribed limits defined above -- namely, the light path between source 141 and detector 148 is interrupted, and the light path between source 142 and detector 149 is not interrupted. This signal indicates that the tape is properly tensioned.

Another status signal is coupled from the vacuum-generating motors (not shown) along a line 6C3 to the CPU indicating, when present, that the vacuum system is not operating. This signal is designated VALM.

V. Control Panel/CPU Interface (Figure 11) The function switch 363 is a muitiposition. rotary selector switch having two decks. The decks are mechanically ganged together, and each deck has at least nine positions, as shown in Figure 9. The wiper arm of one deck is connected in series with the LOAD switch 364C, and the wiper arm of the other deck is connected in series with the DISPLAY switch 364A.

The outputs of the function switch (in combination with the LOAD and DISPLAY switches) together with the outputs of the other control panel switches are fed to a series of six encoders. generally designated by reference numeral 436 and individually designated 436A-436F respectively. The encoders 436 may be part No. 74LS148 of Texas Instruments.

The coded outputs of the encoders 436 are fed, as illustrated in Figure 11. to three NAND gates (designated 438A-438C respectively) and to an encoder 439. The outputs of the NAND gates 438A-438C are coupled respectively to one input of three OR gates 440A-440C. The least significant bit of encoder 439 is coupled through an inverter 431 to one input of an OR gate 440D; and the other two outputs of the encoder 439 are connected to inverters 440E and 440F. Encoder 439 indicates to the CPU on lines 8A4-8A6 which of encoders 436 has been activated. The outputs of the circuits 440A-440F comprise respectively the data lines of the previously described bus 8A (Figure 1) and they are designated respectively 8A1-8A6. The seventh line of the bus, namely 8A7 comprises the "data present" line and it is an interrupt of the CPU. The signal is a pulse from a contact debouncer 442 which may be, for example, a Motorola MC14490. It debounces the signals from all the pushbuttons.

Contact debouncer 442 provides at one of its outputs an enable signal to encoder 439 after responding at its input to an indication that one of encoders 436 has been activated.

Thus, encoder 439 transfers its coded output to lines 8A4-8A6 only after contact debouncer 442 has performed its function in eliminating possible errors from spurious contact bounce signals. The latter receives its input from EXCLUSIVE NOR gate 443 having one of its inputs at logic "1" (due to its being tied to +5v), and its other input being fed from EXCLUSIVE NOR gate 444.

EXCLUSIVE NOR gate 444 is fed by the outputs of level converter 445E and encoder 436F. Encoders 436 are connected to each other so that if one has not been activated, it will transmit an enable signal to the next. More specifically, the output of level converter 445E is connected to encoder 436A. If the latter has not been activated by the operator, it will enable encoder 436B which will perform the same function all the way through the chain of encoders to 436F. The output of the latter in combination with the output of 445E (which is normally at the one logic level as discussed below) causes EXCLUSIVE NOR gate 444 to be in a state indicative of no operator initiated encoder activity. Should, however, any of the encoders be activated, the chain of signals is broken and the output of 436F to 444 will change thereby changing the state of EXCLUSIVE NOR gate 444. This change of state is detected by contact debouncer 442 which then performs its above described function.

Shortly thereafter, contact debouncer 442 generates an interrupt signal on another of its outputs to line 8A7. This alerts the CPU to the presence of data on lines 8A1-8A6. The CPU responds to this interrupt in a manner to be discussed below.

Turning now to the upper left hand corner of Figure 11, the data entry switches 362 comprise five individual binary coded decimal switches designated respectively 362A-362E, in order of increasing significance. Each switch may be a pushbutton-controlled switch with mechanical indicators (see Figure 9) which, when enabled, presents on its four output lines, a binary-coded decimal representation of the number to which the associated switch has been preset manually. These switches are strobed sequentially from the highest order switch 362E (representing the ten thousands digit) to the lowest order switch 362A (the units digit). The four outputs of each switch, with corresponding outputs tied together, are connected to the plus inputs of amplifiers used as level converters and designated respectively 445A-445D. A fifth level converter 445E has its positive input connected to a reference voltage, and its negative input connected to a line designated 446F, and comprising one line of a six-line bus 446, received from the lower left hand portion of Figure 12, to be described in more detail presently.

Referring now to Figure 12, and particularly the upper left hand corner, the data bus 8B in Figure 1 from the CPU to the control panel comprises seven data lines designated respectively 8B1-8B7 and one strobe line designated 8B8. The data received from the CPU is in hexadecimal code. The four lines 8B1-8B4 are connected along a common bus to four data inputs of four decoder circuits 450A-450D, as well as to four data inputs of four decoder circuits designated 451A-451D respectively. The decoders are addressed by the data bits on lines 8B5-8B7 which are coupled to a control demultiplexer 452. The decoders 450A-450D may be Motorola part No. 14511; the decoders 451A-451D may be Motorola part No. 14514; and the demultiplexer 452 may be Motorola part No. 4051.

The signal on the strobe line 8B8 is coupled through pulse shaping and delay circuitry generally designated 453 to the control input of the demultiplexer 452.

The decoded outputs of the decoders 450A-450D are connected respectively to the four lower order digits of the previously described five digit numerical display, designated 31 in Figure 2. The individual display indicators are designated respectively 31A-31E. The ten thousands digit is blanked and unblanked (to display a one only) under program control.

The first four decoders 450A-450D are addressed by the first four output lines of the demultiplexer 452 respectively. A "0" signal on the input LE for each of these decoders puts each decoder into a condition for accepting data on its other four input lines; and a "1" causes it to retain the previously accepted data and ignore any changes on its data lines. The decoders 451A-451D are, in turn, addressed respectively by the remaining four output lines of the demultiplexer 452.

The outputs of the decoder 451A are coupled through two quad latch circuits 455A and 455B, to lamp drivers, and then to individual indicator lights on the control panel, as designated. Similarly, the outputs of decoder 451B are coupled to actuate individual indicator lights through a second pair of quad latch circuits 455C and 455D. The quad latches may be part No. 4043 of the previously described manufacturer. Ten of the outputs of the decoder 451C are connected respectively to the indicator lamps associated with the ten different speeds at which an operator is capable of running the tape transport. For referencing each of the indicator lights to an associated switch on the control panel, each light is designated with a number representative of the associated pushbutton, followed by a letter designation.

Decoder 451D has six outputs that are used, and these are connected respectively to the bus lines 446A-446F which were described in connection with Figure 11.

In brief, each of the decoders 450A-450D and 451A-451D is addressed by a decimal number shown in the respective decoder within a block, and representative of the decimal digit corresponding to the three bits on input lines 8B5-8B7, namely, the most significant digit of the hexadecimal code from the CPU.

Vl Operation of CPU/Control Panel Interface Referring to Figure 11, the data entry switches 362A-362E are used for the entry of data (numerical or command) into the system. The switches are used, together with the function switch 363 to identify what the data is and how it is to be used. Briefly, when the CPU detects a data present indication from the interrupt on line 8A7, it accepts the data on lines 8A1-8A6 from encoders 436. If load pushbutton 364C is pressed, it then scans the data switches 362 in their order of significance. Which of data switches 362 is scanned depends on the indicated function, as discussed below. The code used by the CPU to address the function switch encoders 436 and the data entry switches is indicated in the associated functional blocks by a number in a smaller block. The hexadecimal digit 7 on address lines 8B5-8B7 of Figure 12 causes the demultiplexer 452 to enable decoder 451D. The remaining input signals, in this case, are used to address specific locations of the circuitry of Figure 11.

Specifically, the encoders 436 are addressed by hexadecimal code 70 (which transmits a signal along line 446F to level converter 445E, which, in turn, generates an enable signal sent to the encoders 436A-436F and to EXCLUSIVE NOR gate 444). The ten thousands digit switch 362E is addressed by hexadecimal 75, the thousands digit switch 362D is addressed by hexadecimal code 74, and so on as indicated for lines 446A-446D. These address codes are shown within heavy blocks in the associated functional block to which the address relates.

As briefly mentioned above, the signal on line 446F is normally at one digital level, as for example, a "1". This is inverted by level converter 445E to a "0" and fed to circuits 436A and 444 in a manner already treated in detail. Since the signal on 446F is normally at the same level, encoders 436 are always prepared to detect, encode and output any function selected by the operator on the Control Panel. However, when data entry switches 362 are being scanned, operator initiated signal generation at encoders 436 would produce a meaningless or erroneous signal since the encoder outputs would be combined with the switch 362 outputs. Consequently, encoders 436 are suppressed during scanning of switches 362 by changing the logic level on line 446F from "1" to "0". Once scanning of switches 362 is completed, the signal on line 446F is returned to its normal level.

It will be observed that the operator enters various data, such as the location of Beginning of Data or End of Data using the function switch 363, but he also enters the commands at the locations BOD, EOD, BOT and EOT. These are the "user" commands.

Upon the application of power to the recorder, a portion of Random Access Memory is cleared in the CPU. The CPU then clears certain registers and initializes and resets other circuits. The CPU then sends hexadecimal code 70 to the control panel via bus 8B, together with addressing data (hexadecimal code 7) on the address lines 8B5-8B7 for selecting decoder 451D. The decoded output is transmitted via bus 446 (and in particular, line 446F) to the level converter 445E, the output of which enables EXCLUSIVE NOR gate 444 and encoders 436A-436F. Normally, after turning the apparatus on, the next operation is to press the "ready" pushbutton. This generates a hexadecimal code which is coded in encoder 436b and used to actuate the vacuum system and the tape tensioning mechanism, described above.

Assuming that the operator wishes to enter data using the data entry switches 362, the function switch 363 will be set to the desired position, for example, Beginning of Data. By placing the function switch 363 in the BOD position and pressing the load switch 364C, encoder 436E generates a hexadecimal code which, when recognized by the CPU transmits its output through NAND gates 438A-438C and encoder 439 to the OR gates 440A-440D, as well as the inverters 440E and 440F.

The contact debouncer 442 generates a "data present" signal on interrupt line 8A7. The CPU responds to this interrupt and accepts the data as transmitted directly to the CPU via bus 8A.

The microprocessor decodes the information and, under program control, interprets the function code and then generates a hexadecimal code 75 since all five data entry switches must be scanned to enter BOD, as discussed below. This code is transmitted via bus 8B, decoder 451D and line 446E to enable the digit switch 362E representing the ten thousands digit. This information, previously set by the operator, is then transmitted through the level converters 445A-445D to the OR GATES 440A-440D, and to the CPU.

The code in the "load" signal from pushbutton 364C identifies for the CPU which of the five digits available for data entry has to be obtained from the data entry switches 362. A five digit number is used when loading footage, BOD or EOD. A two digit number is used in loading EOT and BOT. A single digit number is used in loading any of the User Commands UCEOT, ECEOD, UCBOD, and UCBOT. Specific storage locations in memory of the CPU are set aside for data from the control panel.

The addressed data entry switches are scanned in order of decreasing significance. After the lowest order switch 362A is read by the CPU, a hexadecimal code 70 is again transmitted to re-enable the function switch encoders 436.

In summary, the circuitry of Figure 11 is used for interrogating the Data Entry Switches by the CPU and for encoding this data, transmitting it to the CPU, and for encoding and transmitting information from the function switches to the CPU. In the latter case, the strobe pulse is used on the "data present" line to interrupt the mainline program and indicate to the CPU that data is available.

Returning now to Figure 12, as indicated above, the information on bus lines 8B5-8B7 is decoded in the demultiplexer 452 to address the decoders 450A-450D and 451A-451D. The decoders 450A-450D are BCD to seven-segment latches for displaying the numerical data.

The outputs of the decoders 451A and 451B are also fed to latches 455A-455D. These latches are used to maintain a lamp in the illuminated state even though an adjacent lamp may be illuminated by the same decoder. A lamp is deenergized, in other words, by sending a complementary signal from the CPU. This is not true, however, for the lamps representing tape speed, so the decoder 451C does not have to feed latch circuits.

The numeric display indicator 31 is normally fed with information indicating footage by the CPU. If, however, the DISPLAY switch 364A is actuated on the control pan whenever tape motion is called for.

In summary, when the operator presses the READY pushbutton, the CPU detects a coded signal on bus 8A (Figure 11) and sends the signal TENT (along bus 6A, Figure 10) to tension the tape. The CPU then initiates a six-second delay between the generation of TENT and the time in which the signal TT (which indicates proper tensioning of the tape) is expected to be received. If the system has not achieved proper tension within the programmed delay time, the system is shut down, and the READY indicator is not illuminated.

B. SPEED SELECTION Assuming now that the operator selects a tape speed by pushing one of the pushbuttons 350, the CPU receives the information by means of the circuitry of Figure 11 and stores in memory the desired speed. After a direction is also specified (forward or reverse), the CPU then transmits a code along bus 6B (Figure 10) representative of a programmed speed of 15/32 ips. These signals are fed to the decoder 400 and thence to the Divide by N circuit 401.

At the same time, the CPU transmits the signal OPRT along line 6A6 to the switch 404, thereby communicating the oscillator 403 with the Divide by N circuit 401. The output of the Divide by N circuit 401 is coupled to the capstan servo 386 which causes the capstan 42 to be driven at the programmed speed prior to the time that the drums are in driving engagement with the capstan.

The reason for driving the capstan at a programmed, low speed prior to engaging the drums is that the preferred puck surface 77 (Figure 5) of the capstan is a high friction, polyurethane resin. If the drums are brought into driving engagement with the capstan while the capstan is not in motion, a "flat" may be formed on the polyurethane puck surface. Since this type of material has "memory", even though the "flat" may last for only one hundred inches or so of tape motion before it is eliminated, it may nevertheless cause flutter.

In summary, the present system causes the capstan to be driven at a programmed slow speed before the drums are engaged, and the programmed speed is independent of the speed selected by the operator. This is under program control by the CPU.

When the capstan has reached the programmed speed the signal LOCK is transmitted from the capstan servo (the signal is internally generated) along bus line 6C6 to the CPU.

The CPU, in turn, then transmits either signal DRCS or DRFS along lines 6A2 or 6A3 respectively to cause the drum positioning motor 371 for the control drum 44 to place the control drum in driving engagement with the capstan 42, by means of the crank shaft 100, described in connection with Figures 4-6. The transport mechanism, as described above, causes the slave drum 40 to follow the control drum after the control drum is in operative engagement (specifically, after the hub 192 has engaged either adjustable stop 286 or adjustable stop 288, and microswitch 260 or 262 has been actuated).

Commencing with the generation of signal DRCS or DRFS, a program delay is initiated by the CPU sufficient to enable both drums 40, 44 to be brought into driving engagement with the capstan 42 as just described. Following the program delay, the CPU transmits the desired speed select data along speed select bus 6B to the decoder 400. The capstan servo 386 will thereupon cause the capstan motor 82 to accelerate until the repetition rate of the signal at tachometer 387 again equals the repetition rate of the input signal, at which time the capstan servo will again generate the signal FLOCK and transmit it along line 6C6 to the CPU.

C. FORWARD/REVERSE When the REVERSE pushbutton is actuated, the system first checks to see whether the tape transport is already operating in the reverse mode.

If, instead, the capstan had been operating in the FORWARD mode, the CPU transmits the programmed speed (15/32 ips) to the tape transport along the bus 6B to slow down the drums. The CPU then initiates a delay until phase lock operation is established at the programmed speed. When the signal FLOCK is received by the CPU, the signal DRCS or DRFS is disabled. This removes torque from the crank shaft motors 370, 371 and permits the drums to move to the idle position in which they are disengaged from the capstan 42. As indicated in connection with Figures 4 and 5, the crank shafts and drums are normally biased to the idle position by the springs 208, 210, 214 and 216.

After a suitable programmed delay, the signals REVR and OPRT are disabled, thereby permitting the drums and capstan to come to a complete stop. The CPU checks to see whether the capstan is in motion (signal CMOT), and if it is, a further delay is induced by the CPU. If the capstan is not in motion and the system is at a complete stop, in the case of entering the REVERSE mode, the CPU again transmits the signal REVR to energize the reverse relay 380 which, by means of the contacts 382, 383, reverses the polarity of power to the power amplifier 385 driving the capstan motor, thereby causing the capstan motor to operate in the reverse direction. At the same time, the CPU transmits data along the speed select bus 6B commanding operation at the programmed speed (15/32 ips).

The relay 380 also causes contacts 381 to transmit the signal REV to the CPU indicating that the transport is operating in the REVERSE mode. The signal REVR may also be used, if necessary, to adjust the supply voltages to the two reel drive motors 421, 418 to equalize the required output torque depending upon whether the system is operating in the FORWARD or REVERSE mode. That is to say, more output torque may be required on the reel drive motor that is taking up the tape than is required on the motor that is metering it out. The supply voltage may be made greater on the motor taking up the tape by means of the signal REVR, and the supply voltage on the motor that is metering out the tape may be correspondingly reduced.

In order to bring the tape transport to the desired speed in the REVERSE mode, the CPU transmits the programmed speed along the speed select bus 6B, and when the signal FLOCK is received on line 6C6, the CPU transmits the desired speed set by the operator, again using bus 6B. The capstan motor is then accelerated in the reverse direction until it achieves the set speed, and the signal LOCK is again transmitted to the CPU.

D. RECORD In the RECORD mode, the operator would have pushed either the FORWARD or REVERSE pushbutton, and then the RECORD pushbutton (all within the group 353 on Figure 10). After the capstan reaches synchronize operation (0LOCK) at the programmed speed (15/32 ips), the CPU transmits one of the signals DRCS and DRFS to engage the drums with the capstan. The CPU then transmits the data representative of desired operating speed along the bus 6B as described above, and after accelerating the capstan and drums, and achieving synchronized operation again, the CPU generates a signal RECD and transmits it to the tape transport along line 6A1. This signal energizes the record relay 373 which energizes the record electronics 376, and at the same time, transmits the signal REC along line 6C7 back to the CPU indicating that the system is in the record mode.

It will be observed that the RECORD operation may be effected independently of the direction of tape movement (forward or reverse).

If the RECORD pushbutton had been pushed between the time that operation is initiated and phase lock operation at the desired speed is achieved, the CPU generates a signal to cause the RECORD indicator to flash. The flashing indicates that recording cannot yet take place. This is one of the codes transmitted to the Control Panel, and it flashes the indicator by sending alternate on and off signals. Once phase lock is achieved, the RECORD indicator remains on.

E. FAST FORWARD/FAST REVERSE It will be observed that there are four mode selector switches 353 corresponding to FAST FORWARD, FAST REVERSE, FORWARD and REVERSE. However, there are only three control signals sent from the CPU to the transport to achieve these controls--namely, OPRT, REVR (the absence of which causes forward capstan motion), and FAST.

To achieve operation in the FAST FORWARD mode, the CPU determines in which direction the capstan is currently operated. If the capstan motion has to be reversed, the capstan is first brought down to the programmed speed as indicated above, the drums are disengaged and placed in the idle position, and then the capstan is stopped.

After the capstan is stopped, the polarity of voltage to the capstan motor is reversed, and the capstan is brought up to the programmed speed in the reverse direction. When phase lock is achieved, the FAST signal is transmitted from the CPU on line 6A7 to energize the fast relay 407 to cause the output repetition rate of the oscillator 403 to be divided by n, which fixes the capstan speed at 320 ips.

The FAST REVERSE mode is entered in a similar manner. That is, the CPU determines the present direction of the capstan motion, and if it has to be reversed, brings the capstan to a stop as indicated above, then brings it up to the programmed speed in the desired direction, and, after a programmed delay, transmits the FAST signal.

If the capstan does not have to be reversed, the CPU, after determining this, simply transmits the signal FAST.

F. ENABLE MODES F1. ENABLE SEARCH When the ENABLE SEARCH pushbutton 356A is depressed, the CPU generates signals (in BCD format) and transmits them along the bus 6B which will cause the capstan to drive the tape in motion at 240ips with the tape in a playback position (signal DRCS). This mode is entered only if the FAST FORWARD or FAST REVERSE pushbuttons are also actuated. The CPU recognizes the ENABLE SEARCH mode, and disables the FAST signal. If the operator had actuated the FORWARD or REVERSE pushbuttons only, the system would not enter the SEARCH mode because the speed set by the operator would govern.

F2. ENABLE TAPE SYNC.

The ENABLE TAPE SYNC signal (TSEN) is communicated from the CPU on line 6A5 when it is desired to control the speed of the tape from a reference signal recorded on the tape. As indicated above, this has the advantage that any perturbation in actual speed of the transport during recording will be reflected on the record of the reference signal which, in turn, may then be used to drive the tape during playback so that the same perturbation will be reflected in the drive of the transport, and thereby reduce the effects of the speed perturbation during recording.

The signal TSEN is fed to the enable circuit 395 which, if a signal is present from the detector 396 indicating that a reference signal is in fact recorded on the tape and being picked up by reproduce amplifier 398, energizes relay 391. Relay 391, in turn, actuates switch 390 and couples the output of the reproduce amplifier 398 directly to the capstan servo 386, causing the capstan servo to be controlled by the reference track on the tape, rather than the capstan tachometer 83. At the same time, contacts 393 return signal TC to the CPU.

F3. ENABLE END OF TAPE If the ENABLE EOT mode is entered (sometimes referred to as ENABLE BOT/EOT since either parameter is continuously updated by the CPU depending on the direction of tape motion), the system will execute any User Command entered at that point. If the mode is enabled and no User Command had been entered, the CPU will execute the Zero Command--i.e. STOP-- as shown in Table I and discussed in greater detail below.

If the ENABLE EOT pushbutton 356B is not actuated and the transport is operating in either the forward or reverse direction, the tape transport will empty a reel. This may be desired either in the FORWARD mode (some tape reels are merely kept in archives without rewinding) or in the REVERSE mode. However, as explained above, if ENABLE EOT is not actuated and the tape is in FAST FORWARD or FAST REVERSE, the CPU will disable the FAST signal at either BOT or EOT when that point is reached and send speed select signals to slow the tape to 120 ips so that the tape is not passed through the transport at the higher speed.

TABLE I FUNCTION VS COMMAND NUMBER USER SHUTTLE ENABLE ON EOT ENABLE ON COMMAND NUMBER UCBOD UCEOD UCBOT UCEOT 0 FORWARD FAST STOP STOP REVERSE 1 FAST STOP FAST FAST FORWARD FORWARD REVERSE 2 STOP REVERSE FORWARD REVERSE 3 FORWARD REVERSE FORWARD REVERSE RECORD RECORD RECORD RECORD 4 SPARE SPARE SPARE SPARE 5 SPARE SPARE SPARE SPARE 6 SPARE SPARE SPARE SPARE 7 SPARE SPARE SPARE SPARE 8 SPARE SPARE SPARE SPARE 9 SPARE SPARE SPARE SPARE The EOT signal is generated in the CPU by comparing the ratio of angular velocity of the reel being emptied (supply reel 16 in the FORWARD mode and takeup reel 18 in the REVERSE mode) to the angular velocity of the capstan motor. This is accomplished by comparing the output pulses from their associated tachometers. It will be observed that there are more capstan pulses from tachometer 83 than there are pulses from the reels. This is because the capstan has a smaller diameter. However, the repetition rate in all three cases is reduced by a divider circuit, as explained above.

The pulses from the capstan tachometer, divided by 200 in circuit 11 (namely the pulses CAP), are stored in a register in the CPU; and this register is reset each time a pulse is received from the reel being emptied (SRP or TUP respectively). Thus, the total number of pulses accumulated in the register at the time of reset is representative of the ratio of the angular velocity of the capstan to the angular velocity of the reel being emptied. This ratio is a number which is representative of the diameter of the tape pack on the reel being emptied. It will be appreciated that the signal is not a true representation of the linear feet of tape remaining because different tapes have different thicknesses. However, it is a representation of the diameter of tape pack remaining; and the present system has the advantage that the EOT position can very easily be reset under operator control, using the data entry switches 362 and the function switch 363. In contrast, prior methods of accomplishing this, as discussed above, have required either the placing of a reflective material on the tape, removing the oxide on the tape with a solvent, or adjusting a light source-photodetector combination.

Although the program resets the register just referred to for each received SRP or TUP pulse, the CPU reads the ratio only every third resetting of the register to minimize the burden on the time available in the CPU and since critical accuracy of the EDT and BOT points is not required.

As indicated, if the EOT signal is on, and there is a User Command entered in the CPU, that command is executed. In this sense, EOT is a generic indicator to define either the End of Tape or Beginning of Tape locations, depending upon whether the supply reel or the takeup reel is being emptied. Execution of a User Command at either location will be discussed presently.

As also explained above, a User Command is a single digit number which may be entered either at UCBOT or UCEOT using the function switch 363, the data entry switch 362 (least significant digit only) and the LOAD pushbutton 364C.

Referring now to Table I, the relationship between the User Command number that is entered by the operator and the specific function performed by the system in response thereto is shown for both modes of "SHUTTLE ENABLE" and "ENABLE EOT". For example, in the case of UCEOT, if the User Command number "0" is stored as UCEOT in the CPU, then the system will stop when the EOT ENABLE switch 356B is actuated and the EOT tape pack diameter is sensed by the CPU. As seen in the right hand column of Table I, additional functions such as "FAST REVERSE", "REVERSE", and "REVERSE RECORD" can be performed depending upon the User Command entered at UCEOT.

The positions indicated as "spare" are not used, but capable of being used for other functions. For example, if recording electronics were used that permitted recording in the reverse direction, the user could record on one track in the forward direction, use a separate command at the EOD point, switch to another track and record in the reverse direction. As another example, the user could actuate a second recording system at the EOD point, and then stop recording on the first system at the EOT point, thereby providing overlap for the final portion of the recording. Further, the user could transfer recording to a second system and then run the tape off the reel on the first recorder, or operate it in fast reverse to rewind the tape.

Unless the system is placed in the ENABLE SHUTTLE or ENABLE EOT modes, the User Commands are not implemented when the tape reaches the BOT, BOD, EOT or EOD points.

F4. ENABLE SHUTTLE Referring to columns 2 and 3 of Table I, the flexibility of the ENABLE SHUTTLE mode will be appreciated since four User Commands are programmed at each of these locations, with the possibility of others.

The "0" User Command at BOT and EOD defines the conventional "SHUTTLE" mode of operation. That is, when BOD is reached, the system normally moves in the forward playback mode, and when EOD is reached, the system moves in a FAST REVERSE mode.

If the other User Commands are employed, when BOD is reached, the system may either be run in a FAST FORWARD (User Command 1), STOP (User Command 2), or FORWARD RECORD (User Command 3).

If no other command is indicated by the user and the ENABLE SHUTTLE switch is actuated the "0" commands are used so that the system operates in the normal SHUTTLE mode.

Thus, when the "ENABLE SHUTTLE" switch 356 is depressed, the CPU continuously updates the footage count as signals are received via the interrupt signal CAP (one pulse per each 1/100 foot of tape travel). When the actual footage reaches the locations defined by the user as BOD or EOD, the CPU retrieves the User Command which the operator has indicated is to be executed, for that particular position (EOD or BOD), sets a flag indicating that a new command has been received, and proceeds to execute that command.

That command is executed just as though it were received from the control panel.

Specifically, the CPU generates an instruction code which is identical to the code that would have been generated if the command had been implemented at the control panel. This instruction code is used to execute the commands.

G. MISCELLANEOUS MODES G1. ADVANCE TO BEGINNING OF DATA (TO BOD) When the "TO DATA" switch 354 is depressed, the CPU determines whether it has to implement a FORWARD or REVERSE command (always at the fast speed) depending upon whether the footage indicated for the present location is greater than or less than the footage for BOD.

Each time the location defined as BOD is crossed, the motion of the tape is reversed and the speed is reduced incrementally, the increments being defined by the permissible speed of the speed selector switches 350 (see the control panel of Figure 10). Thus, if BOD is crossed in the REVERSE mode at 120 ips, the transport is caused to operate in the FORWARD mode at 60 ips, and this hunting for BOD continues until ,the location is reached at the lowest speed, and the system stops.

G2. SRP, TUP The signals SRP and TUP, as explained above, are interrupt signals transmitted to the CPU on lines 6D2 and 6D3 respectively (Figure 10) from the tachometers for the reel motors 421, 418. Each interrupt indicates one complete revolution of the respective reel.

These signals, in combination with the contents of the aforementioned register in the CPU determine the ratio of angular displacement between the capstan motor and the reel motor as explained above. These signals are used to define End of Tape and Beginning of Tape positions.

The End of Tape and Beginning of Tape positions can be changed by the entry of a two-digit number by means of the control panel. Specifically, the data entry switches 362 (two lowest order switches), the function switch 363, and the load switch 364C are used to enter BOT and EOT locations. These locations, as explained above, are ratios which are not dependent on motor speed and which define tape pack diameter for the reel being emptied, rather than linear footage remaining.

G3. FOOTAGE The numerical display indicator 31 normally displays footage locations, and is continuously updated by the CPU which receives an interrupt signal (CAP in Figure 11) for each 1/100 foot of tape displacement from the capstan motor tachometer 387. The footage data can be reset to zero by pressing the pusbutton 364B, regardless of the setting on the Data Entry switches or the position of the function switch. Further, the operator may, at any location, enter a footage representation by using the function selector switch 363 (set to the position labelled FOOTAGE), entering the desired footage in the data entry switches 362, and depressing the LOAD pushbutton 364C. The CPU will store the new footage indicator in the footage storage location, and thereafter, the CPU will update this number.

Hence, all subsequent footage indications will be referenced to the new setting. Thus, other events of interest can be made to occur at the footage indications given in a written log or indicated on an accompanying voice track, thereby eliminating footage displacement calculations.

G4. CALIBRATION By pushing the CAL pushbutton 355, a calibration signal is recorded on the tape, provided the tape recorder is in the RECORD mode. The length of calibration burst is controlled by the length of time the switch is operated. As with other switches, a visual indicator is also provided.

Attention is directed to our co-pending Patent Applications No. 16063/77 (Serial No.

1602444), No. 8028515 (Serial No. 1602446) and No. 8028516 (Serial No. 1602447); and also to our co-pending Patent Application No. 14961/78 (Serial No. 1602445) which describes and claims the tape transport mechanism referred to at II above.

Claims (5)

WHAT WE CLAIM IS:

1. A method of controlling the operation of a tape recorder having first and second reels for storing tape, transducer means, and transport means for transporting tape from one of said reels in predetermined relation with said transducer means onto the other of said reels, said transport means comprising a capstan, capstan drive means for driving said capstan responsive to speed select signals and further responsive to a feedback signal representative of the speed of said capstan motor for generating a phase lock signal when the speed of the capstan corresponds to the speed setting determined by said speed select signals; first and second drums, said tape being trained about said drums in wrapping engagement; means for moving said drums between a read position in which the tape span supported between said drums is in operative relation with said transducer, an idle position in which said drums are disengaged from said capstan, and a transport position in which said drums are in driving engagement with said capstan and said tape span is not in operative relation with said transducer, said method comprising: storing first speed select signals representative of a tape speed selected by an operator; transmitting second speed select signals to said drive means for operating said capstan at a predetermined, programmed slow speed; detecting said phase lock signal when said capstan is operating at said programmed speed while said drums are in said idle position; generating a control signal to place said drums in driving engagement with said capstan; and then transmitting speed select signals representative of the speed selected by said operator to drive said capstan drive means at the selected speed.

2. The method of claim 1 wherein said first and second drums comprise a control drum and a slave drum, said tape recorder further including first and second mounting means for moving said drums respectively in arcuate paths between said transport position, idle position, and read position; and means for actuating said mounting means for said slave drum in response to the positioning of said control drum; said method further comprising the steps of transmitting said control signal after it is generated to control the positioning of said control drum in one of said transport and read positions; delaying a preset, programmed delay time to permit said slave drum to be correspondingly positioned; and then transmitting said operator speed select signals to said capstan drive means.

3. A method of reversing the direction of tape motion in a tape recorder having first and second reels for storing tape, transducer means and transport means for transporting tape from one of said reels in predetermined relation with said transducer means onto the other of said reels, said transport means comprising a capstan, capstan drive means for driving said capstan responsive to speed select signals and further responsive to a feedback signal representative of the speed of said capstan motor for generating a phase lock signal when the speed of the capstan corresponds to the speed setting determined by said speed select signals; first and second drums, said tape being trained about said drums in wrapping engagement; means for moving said drums between a read position in which the tape span supported between said drums is in operative relation with said transducer, an idle position in which said drums are disengaged from said capstan, and a transport position in which said drums are in driving engagement with said capstan and said tape span is not in operative relation with said transducer, said method comprising: storing signals representative of the present speed and direction of tape motion; storing first speed select signals representative of a tape speed selected by an operator; transmitting second speed select signals to said drive means for operating said capstan at a predetermined, programmed slow speed in the present direction; detecting said phase lock signal when said capstan is operating at said programmed speed while said drums are in driving engagement with said capstan; then disengaging said drums from said capstan; then de-energizing said capstan drive means; then energizing said capstan drive means in the reverse direction; then transmitting said second speed select signals to said drive means for operating said capstan at said programmed speed in the reverse direction after said capstan has stopped; detecting said phase lock signal when said capstan is operating at said programmed speed in the reverse direction with said drums disengaged from said capstan; generating a control signal to place said drums in driving engagement with said capstan; delaying a preset time; and then transmitting speed select signals representative of the speed selected by said operator to drive said capstan drive means at the selected speed.

4. A method of controlling the operation of a tape recorder at a selected tape speed, substantially as hereinbefore described with reference to the accompanying drawings.

5. A method of reversing the direction of tape motion in a tape recorder, substantially as hereinbefore described with reference to the accompanying drawings.