US2756275A - Multistation remotely-controlled phonographic system - Google Patents

Description

y 1956 w. w. LOGAN 2,756,275

MULTISTATION REMOTELY-CONTROLLED PHONOGRAPHIC SYSTEM Filed March 11, 1955 10 20 I. F 64w T i 65 9 1 162 65 =3 i i i E1 l 27 I i 23 INVENTOR William W. Logan United States Patent MULTISTATION REMOTELY-CONTROLLED PHONOGRAPHIC SYSTEM WiHiaInWrLOgan, GlenRidge, N. J., assignor to Thomas A. Edison, Incorporated, WesLOrange, N. J., a corporation of New Jersey ApplicationMarch 11, 1955, SerialNo; 493,657"

6 Claims. (Cl. 179-1001} issued-Aprilv27, 1954. In thedictation recording system.

disclosed in-this patent the branch circuits of the interstati'on connecting means are. connected to acommon powerasuppl-y having; poor-voltage regulation, and in eachbranchcircuitthere is a; privacy relayfor: the respectiveremote stationwhichis normally in" acondition to prevent. operation: of. the: phonographic system from". that station.- However, as; the firsttof thesseveral'stations is. connectedto: the machine the respective privacy relay is operated; by the: voltage then' available from the'power supplyzto. render that station effective for recording and/ or reproducing dictationv on or from the-machine; However, the loadzplaced on' the'powersupply'by such:first' station-causes: theevoltage. in the branch circuits to' fall:

to a level'insufii'cient' to operatethe privacy relay of. a

second! station: when: that station is. also connected to the; machine, with the result that: Whenever: any first station is once connected to the machine no second'stationcan be'rendered operative'either to listento the dictation of the user of the system or to interferewith his control thereof.

An object of my invention is to provideimprovements by which privacy to the userofsuch remotely cont'rolled phonographic system is attained more dependably and efiiciently.

Another object isto' provideimprovements in: such systems whieh will provide a greater differential'of op erating control ibet'ween the privacy relay of a station in use and the privaey'relay ofa second or intruding station.

Another object isto provide improvements in: such systems whereby privacy" is obtained dependably without interference under any condition with the normal control of"the=-system by the user.

The-improvement of 'the presentinventionresides particularly in the provision of anon-linearimpedance in each branch circuit' 'which has an impedance characteristic variable inversely withapplied voltage such that it presents a low impedance in'the circuit when'the voltage is high and'a-higher-impedance when thevoltage is low. Ihthis connection, a specific'object ofthe invention .is to short'out the non-linear impedance correspondingto the station in' use -by-therespeetive-privacy relay as-tha't relay is operated to render the'machine operable. from that station.

These and' other objects and features of my invention willbe; apparent: from following description; and: the? appended claims:

In the description of my invention reference is had to 2,756,275 Patented J 1:1 24, 1956- 'ice 2; the accompanying figure. showing diagrammatically a multistation remotely-controlled phonographic systemincorporating. my invention.

For purposesv of simplification, onlysuch portionof-a dictation recordingsystemis shownimthe accompanying figure as need be considered for the: purposesv of the present invention.

The dictation recording system comprises an attendants station 10 and a plurality offident-ical remoteopi erato'rs stations of which there are two :shown by way 0% example; referred to respectivelyas 11a and llbl; At the attendants station thereis a; dictating machine: 12 (fractionallyshown) which: comprises a turntable 13: driven by a-motor 14-through aclutch 15. The turntable carries a record: disk 16 engaged -a=recording" unit. 17." Audio-speech representing currents are fed to. this res cording unit through an audio transformer: 18 and at circuit 19 including an amplifier 20.

The attendants station is provided witha communi cation and. control circuit Zi -sometimes referred to as the main circuit OfthG'llIItEI'StatlOH' connecting:means which serially includes" the primary of the: audio transformer.18. For'the'control purposes. just mentioned; this circuitiincludes two serially connected relays z2 and 23f Audio currents in this circuit are by-passed past: these relayssby. a condenseri24. Thismain circuit is energized from a low-voltage D .-C.' power source (not shown) which is connected to-th'e: terminals 25 marked plus=anc minus. respectively. The relays areadapted to operate at different levels of D-.-C. current established" selectively at the operators stations as will appear. Therelay- 2-25 has contacts 2'6 operated at th'e'lower current level toclose a power circuit z'Tse-rially including the motor 14% This power circuit is energized=fr0nr an A.-C. source (not shown) which is to be connectedto the terminals 28. The second relay- 23 is adapted to operate. at a higher levelof'current and controls the clutch-1 5 as-rep resented diag'rammatically by-the line 2321. These relays may of. courseperform other control functions which need not however-be herein'd'e'scribeda' For the present purposes,- it'will be understoodthat the motor-'1 is started when the relay-22 is-operated and that theclutch' 15 'is' engaged to' start rotation of the -turntable 13*wherrthe' relay 23'-'is operatedi An-energization of' themai'n' circu-it' 21 at the lower current level, with the resultant" starting of'the motor14;ishereinconsidered'as an activation of'the dictating system:

In'the power circuit 27 and in' shuntwith'the motor-l4 there' is a voltagestep=down transformer'29 the secondary of which is connected to two outgoing-leads constituting a signal circuit30 -for the dictating system. This signal circuitis accordingly energized whenever the" dictating system'is activated; 7

The operators stationsl'la and 1-11: are identicaland a description of one will suifice' for both. Branchcir cuitsilead" from the main circuitZl to theseremotestations' respectively, which branch circuits are' referred: toby; the numeral 21 with the suflix letter of the respective station. Likewise, branch'signal circuits leadfrom the mainsigna-l'ciicuit 30 to each remote station-referredto by thenmneral 30 with the suflixletter of eacli remote station.

The station 11a includes a handpiece'31a; for'example', of the usual telephone variety having, astransducer ele ments, a carbon buttonvmicrop'ho'ne 32a; and receiver: 33a: each of which is connected: across the: respective: branch circuit 21a zwhe'n theiremote' station-isconditioned to activate the: system". forruse; Also,- the remote! station" has an. on-otf; station switch'34asof the double pole twm position-type, one pole 35a 10f WhiChlSE'COHHGClIfid tothe negative side ofethe'branch circuit 21a. and the -,othertpolei 36a of which is connected to the positive side. The station switch is biased closed (into on position) by a tension spring 37:: but is held open by weight of the handpieceplaoed as on a hooked extension 38a of the pole 36a when the station is not in use.

The branch signal circuits serially include respective signal lamps at the remote stations. referred to by the number'39 with the sufiix letter of the respective station. These lamps provide a busy signal at each remote station when the phonographic system is activated for use.

The station 11a is provided with a' three-hole privacy relay 40a which disables the station when the relay is in its normal position. The coil of this relay is connected seriallyin a line 41a leading from a contact 42a associated with the pole 36a to a contact 43a associated with the pole 35a. When the station switch is closed, the voltage from the power supply 25 is applied across the coil of the relay. As will appear, if the station 1111 is the first of the several stations so connected to the machine by the respective station switch, the privacy relay 40a is activated. When so activated, the pole 44a thereof is moved to engage contact 45a, the pole 46a is moved from contact 47a to contact 48a, and the pole 49a there-. of ismoved from contactStla to contact 51a. iThe effect of pole 46a making with contact 48a is to connect the line 41a at the positive side of the privacy relay to one side of the receiver 33a by way of a lead wire 52a, the contact 48a and pole 46a and a lead wire 53a serially including a resistor'54a and condenser 55a. Similarly, the line 41a at the positive side of the privacy relay is at the same time rendered connectable to one side of the micro-' phone 32a by way of a branch circuit 56a leading from the line 53a and serially including a start-stop switch 57a. The effect of the pole 49a making with the contact 51a is to connect the line 4111 at the negative side of the privacy relay with the other sides of the receiver and microphone by way of a lead wire 58a, pole 49a, contact 51a and lead line 59a. Thus, the activation of the privacy relay following'the closure of the station switch connects the receiver across the branch circuit 21a through the resistor 54a and condenser 55a and also it renders the microphone connectable across the same branch circuit by way of the start-stop switch 57a.

The current which flows through the'privacy relay when the station switch is closed serves to operate the relay 22 to close the power circuit to the motor 14 .as well as to supply power to any other components necessary to condition the machine for immediate start-stop operation but which need not be herein described. When the start-stop switch 57a is closed, a second circuit through the microphone is completed across the branch circuit to cause the level of direct current in the main circuit 21 to be increased with resultant operation of the relay 23 at the attendants station to close the clutch and start record rotation.

Because of the resistance of the relay coils 22 and23 and of the primary winding of the audio transformer 18 in the main circuit 21, the voltage available to the branch circuits has poor regulation causing it to fall substantially. when any one of the remote stations is connected to the machine. The voltage-operating characteristic of these privacy relays is such that each requires a relatively high operating voltage and a low holding voltage. Thus, a privacy relay will operate from the current surge available, especially from the charged condenser 24, when the first us'er closes his station switch, and will be retained in operated position at the lower supply voltage which is available after the station switch is closed. This lower supply voltage is however insufiicient to operate any second one of the privacy relays as when the station switch of a second remote station is connected to the machine. Thus, if a second prospective user closes his station switch while the machine is in use from a first station, his privacy relay will not be operated with the result that his station equipment-i. e., his receiver and microphone transducers and control switches-are not connected et- 4 fectively to the machine either to enable him to listen to the users dictation or to exercise any control over the machine. 1

The failure of the privacy relay to operate at the second station just mentioned is utilized to provide a heavy hum or signal in the receiver at that station so as to apprise the second would-be user that the system is being used by another and that his station is in a disabled condition. This signal is fed to the receiver from the respective branch signal circuit. For example, if the operator at station 11b lifts his handpiece while the operator at station 11:: is using the system, the signalcircuit from the branch 3% to the receiver 33b is completed via contact 5011, pole 4%, line 58b, receiver 33b, circuit 53b including the condenser b and resistor 54b, pole 4617, contact 47?) and lead line b.

When the phonographic system is activated say from station 11a, the user is enabled to record dictation spoken into his microphone and is enabled also, at will, to reproduce portions of his recorded dictation. For recordation, the user presses and releases the switch 57a to start and stop the machine. To reproduce, he presses a separate switch 61a. When this switch is closed, a relay 62 is operated at the attendants station. connected by a line 63 between the positive side of the main circuit 21 and one side of the signal circuit 30 to receive operating current from the potential source 25 by way of the line 63, one side of the main signal circuit 30 and of the branch circuit 30a, switch 61a, pole 49a, contact 51a and the negative side of the branch circuit 21a and main circuit 21 to the negative side of the potential source 25. The relay 62 controls a double-pole switch 64 and the clutch 15. The switch 64 is normally positioned to connect the audio transformer 18 to the recording amplifier 20. As the relay 62 is operated, the

switch 64 shifts the connection of the audio transformer to a reproducing amplifier 65 in a line 66 leading to a reproducer 67. This reproducer engages the record at a trailing distance behind the recorder. Thus, as the reproducing control switch 61a is closed the machine is conditioned for reproduction and record rotation isstation switch is closed to connect the respective privacy relay to the power supply may be of the order of 30 volts, and the voltage at the remote stations when the start-stop switch 57 is also closed may be only 5 volts. The resistance associated with the voltage source may be of the orderof 300 ohms and that of each privacy relay of the order of 700 ohms. Each privacy relay should be of a type that will pull in-i. e., operate-at an applied voltage of the order of 30-volts and will hold in-i. e., stay operated-at an applied voltage of the order of only 4 volts. 1

In the system so far described there is required very careful selection of the regulation characteristics of the power supply 25 as well as of the operate characteristics of the privacy relays and of the start-stop relay 23 in order to assure dependable operation without interference between stations. This difliculty arises particularly because of the use of-current level control in the circuit 21 for operating-the start-stop relay 23. For instance, when a second station operator closeshis station switch while the system is in use, he connects his privacy relay also across the main circuit 21 in parallel with the users privacy relay. Although the voltage in the circuit 21 is not.

now suflicient to operate the second privacy relay, the

additional load presented by the second privacy. relay may cause interference with the normal operation of the start- The relay 62 isstoprelay 23. The additional load'may for example be suiii'cient to prevent drop out' of the start-stoprel'ay 23- when. the user: releases his start-stop button57. Such failureof the start-stop'relay to drop outwouldemeanof: course. that the record rotation. would continue, with Waste of space on the record, while the user was under the impression that the record was at standstill. Furthermore, if one or moreprospective users: should close their. station switches attthe same time, the increased'currentdrainon the power supply would be.all the more apt. to keep the start-stop relay in operate position when the user releases his start-stop button and would evencause the start-stop relay to operate should the user thenhave his start-stop switch released, with resultant waste. of record spacein either case.

The purpose of the present invention is to prevent the foregoing possible misoperations; This is accomplished by the provision ofsimple means at'each remote station which is differentially responsive according to the-voltage" available to the branch circuits. This-means' may simply be anon-linear impedance or resistance 70 of the type which is inversely voltage-sensitivei.e., has" alow resistance at high applied voltages and a high resistancezat: low applied voltages. Such resistance element, known commonly as a varistor, may be a rectifier, for instance a selenium rectifier, connected in such polarity relative to the D.-C. source 25 that it is operated in its inverse voltage range; or alternatively, it may consist of a nonpolarizing type of voltage-sensitive non-linear resistance such as is well known in the art.

When the voltage available to the remote stations is high--such as exists when a remote station, say station 11a, is first connected to the machine-the respective varistor 70a connected in series with the privacy relay 40a will have a low resistance which, with proper adjustment of the circuit and voltage values, will not interfere With the normal operation of the respective privacy relay as the station switch is closed. As the privacy relay is operated, the pole 44a thereof makes with the contact 45a to short out the varistor. With the varistor being shorted out, the load of the privacy relay 40a is great enough to cause the supply voltage to have a sufiiciently low value, due to its poor voltage regulation, to be insuificient to operate any second of the privacy relays should another station switch be closed. At the same time, this reduction in voltage supply is such that when any second varistor is connected to the main circuit by the closing of the respective station switch, the resistance thereof will be relatively high. Due to the higher resistance of the varistor at the other station, this other station presents very little additional load on the main circuit 21. The very small additional current which flows when the second station is thus connected to the machine not only assures a wider margin of safety against operation of the privacy relay of the second station but also assures that the normal start-stop control of the system is not interfered with.

Typically, when no varistors are used in the present system the current available to a second or intruding station is of the order of .66 of that available in the first instance to the first users station, but when varistors are used the current available to the intruding station is of the order of only .32 of that available to the first users station. Thus, with my invention an advantage is gained representing a factor of 2 or more. Because of this greater margin of safety, a relatively greater number of additional stations could be connected to the main circuit while the system is in use without these additional stations raising the current drain to the prescribed level required to operate the start-stop relay 23. Also, because the current drain of each station is smaller the chance of operation of a privacy relay at a second station is reduced.

The foregoing description of my invention is intended to be illustrative and not necessarily limitative of my invention since the same is subject to changes and modiswitches connected to said branch circuits'and movable iii-- to. efiective and" ineitective' positions for rendering; mop-- erative and-operative therespective'remote stations; re spective electrically-energizable devices 'for' operating saiddisabling switches normally conditioned to render the stations inoperative andconnectedin'the'respective-branch circuits for operation by saidpotential source to render? the. respective stations'operativeupon closure of" the re spective'station switches;.means connected'in circuit'wiflr said potential sourceand elfectiveupon closure of one of said branch circuits for reducing the voltage 'tosaid branch circuits to a value insuflicient to operate any subsequent one of said energizable devices; and a non-linear impedance in each of said branch circuits having an impedance inversely variable to the voltage applied thereto within the range of voltages available from said branch circuits.

2. The combination set forth in claim 1 including a respective switch for each non-linear impedance operable to short that impedance; and means to cause operation of the respective shorting switch when the respective energizable device is operated.

3. In a remotely-controlled multistation phonographic system including a source of direct current potential: the combination of an attendants station including a phonographic machine; a plurality of remote operators stat'ions each including a transducer and an on-ofi station switch; circuit means including respective branch circuits leading from said remote stations respectively for connecting a remote station to said machine when the respective station switch is closed; means connecting said potential source to said circuit means for supplying energizing potential to each of said branch circuits; resistance means connected in circuit with said potential source to cause a substantial decrease in the line voltage at the remote stations when one of said branch circuits is closed; respective disabling relays for said remote stations normally in disabling condition and connected in the respective branch circuits for operation by said potential source as the respective station switches are closed, each of said relays having a voltage characteristic such that it is operable by the open circuit line voltage existing in said branch circuits when the first of said circuits is closed and such that it is inoperable by the line voltages at the remote stations when another one of said station switches is already closed; switch means in each relay for connecting the respective transducer to said machine as the relay is operated; and a non-linear impedance for each remote station connected in series with the respective disabling relay, each of said non-linear impedances being adapted to have a low impedance when connected in circuit with the line voltage existing in said branch circuits at the time the first of said branch circuits is closed and to have a relatively high impedance when connected in circuit with the line voltage existing in said branch circuits at the time one of said branch circuits is already closed.

4. The combination set forth in claim 3 including capacitance means associated with said potential source to provide a current surge available when the first of said branch circuits is closed to operate the respective disabling relay; and including means to remove efiectively the respective nonlinear impedance from the respective branch' circuit .when the respective disabling relay is operated. I

5. In a remotely-controlled multistation phonographic system comprising a source of potential and a phonographic machine having record translating apparatus and drive means for operating said translating apparatus: the combination of a plurality of remote stations including on-ofi station switches respectively; interstation connecting means comprising a main circuit connected to said potential source and branch circuits leading therefrom to each remote station for connecting the station to said phonographic machine when, the respective station switch is closed; a start-stop energizable device in said main circuit for starting and stopping said drive means, said start-stop device being adapted to operate when a prescribed level of current is reached in said main circuit; current level control means at each remote station for establishing said prescribed current level to start said drive means; a privacy-relay at each remote station connectable across the respective branch circuit by the closing of the respective station switch; means associated with said power source to cause a substantial drop in the voltage supply to said branch circuits when one of said stations is connected to said machine, each of said privacy relays being normally in position to disable the respective station and being operable by theinitial voltage available to said branch circuitstwhen the first of said stations is connected to the machine wherebyto render the machine operable from said first station, said privacy relays having a voltage characteristic causing the relay to'be inoperable by the lower voltage supply available to said branch'circuits when one of said stations has already been connected to said machine; and a non-linear voltage-sensitive impedance in series with each of said privacy relays having a relatively low impedance at higher applied voltages enabling operation of the respective privacy relay when said first station is connected to the machine and having a higher impedance at lower applied voltages adapted to reduce the current drain on said main circuit to prevent the current in said main circuit from reaching said pre scribed level when a plurality of additional stations are also connected to said machine.

6. The combination set forth in claim 5 including means operable by each privacy relay to short out the respective nonlinear impedance as the privacy relay is operated.

a No references cited.

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