US2143971A

US2143971A - Telephone system

Info

Publication number: US2143971A
Application number: US133465A
Authority: US
Inventors: Brazelton Roy Melville
Original assignee: American Telephone and Telegraph Co Inc
Current assignee: AT&T Corp
Priority date: 1937-03-27
Filing date: 1937-03-27
Publication date: 1939-01-17
Anticipated expiration: 1956-01-17

Description

2 Sheets-Sheet l EH W? W5 lNl/ENTOR RM. BRAZE TON BVfl WI? TELEPHONE SYSTEM R. M. BRAZELTON Filed March 27, 1957 Jam 17, 1939,

h. wt

ATTOR/VEV Jan. 17, 1939. R. M. BRAZELTON TELEPHONE SYSTEM Filed March 27, 1957 Sheets-Sheet 2 lllllllll ll III IIIII I llllllll A 7' TQRNE V Patented Jan. 17, 1939 UNITED STATES PATENT orrics TELEPHONE SYSTEM Application March 27, 1937, Serial No. 133,465

16 Claims.

This invention relates to telephone systems and particularly to systems in which directively controlled electro-magnetic switches are used in establishing desired connections.

It is the object of the invention to improve the quality of the service rendered and moreover at the same time reduce the maintenance effort in automatic telephone systems of the type in which the switches are directly controlled by digit impulses from the calling station.

In automatic telephone systems in which registers are provided for receiving the directive impulses from calling stations it is usual to provide for automatically connecting a subscribers line to an operator in case impulses are not received by the register within a predetermined interval of time, such as thirty seconds, after the register is connected to the line. By this arrangement, a large part of such cases are promptly disposed of and the lines restored to service by the operator without requiring any attention by the switch room or test-room attendants; and it is necessary to trace the call and identify the calling line in comparatively few cases. I-Ieretofore in systems in which registers are not provided and the switches are directly controlled by the impulses from calling stations, it is usual to provide a permanent signal alarm which is effective, a predetermined interval, such as twenty minutes, after a line is connected to a first selector and no directive impulses have been received, to summon a maintenance attendant who thereupon traces the call and frees the line-finder and selector switches from the line. According to this invention an arrangement is provided in an automatic telephone system. in which the directive impulses from calling subscribers stations are received by switches through which desired connections are established, for automatically connecting a calling line, from which no directive impulses are re ceived within a predetermined interval, such as thirty seconds after the line is connected to a first selector, to an operator.

According to a feature of i the invention, common timing and control equipment is provided for the first selector switches in an automatic telephone system, with means for automatically attaching the equipment to any first selector in the group upon its connection with a calling line, the control equipment being efiective in case directive impulses are not received by the selector within a predetermined time thereafter to transmit impulses to the selector and operate the se lector to connect the calling line over an idle trunk to an operator. The trunks thus employed may be located on the tenth or zero level or on a level other than the zero level, if such other level is available. An additional feature is the provision of means for stopping the operation of the control equipment, in so far as its connection with a particular group of first selectors is concerned and in case permanent signal calls are routed to an operator over zero level trunks, whenever the maximum allowable number of trunks in the level have been seized and are being held on permanent signal calls.

These and other features of the invention will be better understood by considering the system which is shown schematically in the drawings which form a part of this specification, this systern; being one arranged in accordance with the invention. It is of course understood that the invention is not limited in its application to the particular system shown in the drawings, but

may be applied to any automatic system not otherwise provided with means for automatically routing permanent signal calls to an operator.

Referring to the drawings: Figure 1 shows an automatic telephone ofiice comprising a calling subscribers station A, a

line-finder LF+I and associated first selector switch S--l, other line-finders LF-2l and LF6il and first selectors S'2l and S-=5El in the same group, a connector switch C, a called subscribers station B, a trunk OT-and a manual switchboard M;

Fig. 2 shows a control circuit IC common to all of the first selectors in the ofiice and shows a master-finder switch MF and one finder switch Fl of a group of primary finders by which the control circuit IC is connected to the first selectors one at a time.

The line-finder, selector, and connector switches are of the well-known two-motion stepby-step type. Reference may be had to pages 53 The line-finder switches LFl LF--2l the operation of a step-by-step switch when used as a line-finder. The selector S-i is represented by its set of brushes and two sets of terminals 26 and 2?, the other selectors S2l and Sfi0 are represented by a set of brushes and a single set of terminals. The terminals 26 represent a level of 5:1.

the bank giving access to succeeding selectors or connectors, as the case may be, and the terminals 27 represent the zero (tenth) level through which access is given to trunks leading to zero operator. The trunk OT terminates in an answering jack 33, and since in this case the same group of trunks is also used for permanent signal calls, the auxiliary jack 36 and associated relays 31 and 38 are provided for use and operation on such calls. The operation of the selector S1 and operation of trunk OT are hereinafter described in detail.

The finder switches such as FI are rotary step-by-step switches each comprising six brushes and terminal banks, there being twentytwo terminals in each bank only twenty of which are used in the arrangement shown. Each pair of brushes gives access to twenty first selectors, there being two conductors from each selector which conductors connect to like numbered terminals on two of the banks. For instance, conductors 4i and 42 from selector S--I are connected to terminal I in each of banks I and 2 of switch F-I,

conductors

43 and 44 from selector S2I are connected to terminal I in

banks

3 and 4, and conductors 45 and 46 from selector S6ll are connected to terminal 20 in banks 5 and 6. Thus each finder switch, such as F-I, gives access to a group of sixty first selectors. The master finder switch MP is also a 22-point rotary step-by-step switch, each of the three brushes and banks of which serves to connect the control circuit IC to 22 primary finders, thereby providing for the connection of the control circuit IC to a maximum of 1320 first selectors. It is, of course, understood that finder switches of other types and having a different number of brushes and banks and a difierent number of terminals in a bank may be provided, and thereby give access to whatever number of first selectors there may be in the oflice in question. The conductors 4|, 43, 45, etc., are each connected to the front contact of the line relay of the associtaed selector; so that, when the line relay operates, it connects ground to this conductor; and, when the first dial impulse is received, the release of the line relay opens this connection. The other conductors such as 42, 44 and 4B are each connected through the winding of the change-over relay to the winding of the vertical stepping magnet of the associated first selector.

The primary finder switches such as FI are normally hunting for selectors which have been seized and not yet moved off normal. The circuit for operating the stepping magnet 50 of finder FI is traced through the back contacts of relays 55, 53 and El and through the impuse-per-minute interrupter 51 to ground. When a finder switch such as FI finds the terminals of a. selector which has been seized but not yet moved off normal the ground potential over the conductor such as 4| is effective to operate a relay such as relay 5|, to stop the finder on these terminals, and tostart the energization of a timing relay, such as relay 52, the operation of which requires an interval of roan 30 to 60 seconds. If the selector is moved ofi normal before the expiration of this interval, the hunting operation of the finder switch is resumed; but if the selector is not moved ofi normal before this interval has expired the timing relay is operated and the master finder switch MF set in motion to connect the control circuit 10 to the conductor such as 42 from the selector in question. The control circuit IC is thereupon efiective to transmit impulses over this conductor to operate the vertical-stepping magnet of this selector and raise the. brushes to the zero level or to any other desired level. The impulses are created by the operation of an impulse mechanism comprising the motor H10, cams IIJI, I03 and H35, and contacts I62, I04 and H16. The 10 pulse cam I03 and trip cam I05 are mounted on the same shaft to rotate together; but impulse cam IOI is geared to make eighteen or twenty revolutions to one revolution of cams I03 and IE5, the contact I02 being closed ten times by cam it! during the interval that contact I54 is closed by cam 553.

The operation of the finder switches and common timing and alarm mechanism will be further described by assuming the connection of the selector SI to a calling line. The receiver having been removed from the receiver hook at a calling station A and the line I0 having been connected by operation of the line-finder LFI through its brushes to the line relay II of the associated first selector S I, relay II is energized. Relay II closes a circuit for operating e release relay i2 and relay I2 connects ground to sleeve conductor l9 to hold the line-finder switch LFI and the cut-off relay (not shown) of line it in usual manner. Relay 25 of the common alarm circuit is energized in series with relay I2 and starts the operation of the usual timing equipment whereby a maintenance alarm will be given within an interval of about twenty to forty minutes. When relay II operates, the ground at the uppermost back contact of relay I4 is connected to conductor 4| and, as soon as brush I of finder switch F-I encounters the terminal to which conductor 4i is connected, relay 5| operates thereby preventing the further operation of stepping magnet 5!). Relay 5i closes a circuit for energizing the timing relay 52. Relay 52 is designed to operate within an interval of from thirty to sixty seconds after its operating circuit is closed; and, if the line relay of the selector releases (in response to the first dial impulse) prior to operation of relay 52, relay 5| releases and the hunting operation of the finder switch F-I is resumed. In this case the selector Si responds to the dial impulses in usual manner to select a desired level of the bank and an idle set of terminals in the selected level. The call is thereafter completed through a connector switch such as C to a called line B in usual manner.

If, however, the calling subscriber fails to dial. or if some trouble condition has given rise to the extension of the line I?) to the first selector S-I, relay 52 operates and closes a circuit for operating the start relay tail of the control circuit IC. Relay Eli, when operated, closes a circuit for motor E33 which drives the shaft of the impulse mechanism. If now the control circuit is not in use, a circuit is closed from battery through the winding of stepping relay 6 I, back contact of stepping magnet 62 of finder MF and through the back contacts of relays 9i, 8! and H to ground at the front contact of start relay 5U. Relay 6| connects the winding of magnet 52 to the same ground; when magnet 62 operates, it disconnects relay 6i, and the release of relay 6i disconnects magnet 62 from this ground. Each operation and release of magnet r32 causes the advance of the brushes of switch MF one step, the alternate operation and release of relay 6i and magnet 52 continuing until one of relays II, BI and 9| is operated. Assuming that brush I of switch ME encounters the terminal to which the inner front contact of relay 52 is connected, a circuit is closed from battery through the vertical-stepping magnet IB of selector S;I, winding of relay I3, conductor 42, terminal and brush 2 of finder F--I, inner front contact of relay 52, terminal and brush I of switch MF, back contact of relay I4, and through the winding of relay 1! to ground. The current in this circuit is insufiicient to cause operation of the vertical magnet I6 or changeover relay I3 of selector S-I but is sufficient to operate relay II and thereby stop the advance of switch MF. Assuming that neither of relays 8| and BI is at this time energized in a like circuit, the operation of relay II closes a circuit through back contacts of relays I2, 93, and 33 for operating relay E3. The operation of relay I3 prevents the operation of either relay 83 or 93 until the required operation of the selector, which is connected to relay II, has been completed. Relay I3 also closes an obvious circuit for operating relay I4. Relay M opens the connection between conductor 42 and the winding of'relay 'II, connects this conductor through conductor II2 to the impulse contact IIlZ of cam IilI, closes a holding circuit for relay I! and connects ground through conductor II I to the contacts IM and H36 of cams I03 and IE5. If, when relay I4 operates, the contact I55 of cam I05 is closed, relay IIII cannot operate since its winding is short-circuited by its own outer back contact and contact I05; but as soon thereafter as contact I05 is opened, relay I5! operates through contact I94. Relay IIll' closes a circuit for operating relay IUB. With relay IIJ'I operated, the next succeeding ten closures of im pulse contact I52 transmits a series of ten impulses to the vertical-stepping magnet I5 of selector S-I. This impulse circuit is traced from ground at the front contact of relay I4, over conductor III, through contact I04, left front contact of relay IIl'I, impulse contact I52, conductor IIZ, left front contact of relay I l, brush I and terminal of switch MF, inner front contact of relay 52, brush 2 and terminal of switch F-I over conductor 42 to selector SI, winding of relay I 3, and through the winding of magnet I5 to battery. When the ten impulses have been transmitted contact I 54 opens and relay Ill! re-- leases so that contact I52 is ineffective to transmit any more impulses over conductor H2. The release of relay I ill opens the operating circuit of relay I58; since relay IE8 is slow in releasing a circuit is closed momentarily from ground at the inner back contact of relay Isl, through the front contact of relay Hi8, right front contact of relay "I3 and the winding of relay it to battery. Relay I2 operates and closes a locking circuit through its right front contact to ground at the front contact of relay H. The operation of relay I2 causes the release of relay 13; the release of relay l3 causes the release of relay M; the release of relay I4 causes the release of relay II; and the release of relay II causes the release of relay I2. If, when relay I3 releases, either one of relays BI or BI is operated, the corresponding one of relays I33 and 93 is operated without further operation of switch MF. In this case the associated relays and impulse mechanism transmits impulses over conductor IE2, and through the left front contact of relay 85 or relay 94, to operate that one of the first selectors to which this conductor is connected. If relay I2, 82 or 92 fails to release after relays Ill? and I08 release, ground is connected through the inner back contact of relay Ill'I, back contact of relay I08 and left front contact of relay I2, 82 or 92, over conductor I0 to an alarm circuit.

The first impulse transmitted from the impulse control equipment IC over conductor 42 to selector SI operates relay I3 and magnet I6. Relay I3 is slow in releasing and remains operated while magnet I6 responds to the succeeding impulses in the series. Each operation of magnet I6 raises the brushes one step; and, assuming that ten impulses are received, the brushes are raised to the tenth level. When the shaft and brushes are moved out of normal position, the vertical off-normal springs VON are actuated, closing a circuit for operating relay I5, this circuit is traced fromv battery through the winding of relay I5, lower contact of the VON springs, front contact of relay I3 to ground at the lower front contact of relay I2. Relay I5 closes a holding circuit which includes the back contact of rotary-stepping magnet I'I, its own upper front contact, and the uppermost back contact of relay I. When relay I3 releases after all of the impulses in the series have been received from control equipment 10, a circuit is closed for operating the rotary-stepping magnet I'l; this circuit includes the lower front contact of relay I5, the back contact of relay I3 and the lower front contact of relay I2. Magnet I'I operates advancing the brushes into engagement with the first set of terminals in the tenth level (or other selected level if trunks to a trouble operator are connected to some other level of the bank). The operation of magnet I? causes the release of relay I5; and the release of relay I5 causes the release of magnet I 7. If the trunk connected to the first set of terminals is idle, the cut-through relay I4 is operated when magnet I'I releases; the operating circuit is traced from battery through the winding of relay I5, lower contract of springs VON, back contact of magnet I'I, winding of relay I4, lower contact of the 11th rotary step springs, to ground at the lower front contact of relay I2. Being marginal, relay I5 does not operate in series with relay I4. If, however, the first trunk is busy, the lower brush of switch S-I encounters a ground potential which shortcircuits the winding of relay I4, thereby causing the reoperation of relay I5 instead of the operation of relay I6. Relay I5 again closes the circuit for operating magnet II and the brushes are advanced to the next set of terminals, the above-described cycle of operation of relay I5 and magnet Il being repeated until an idle trunk is found at which time relay I4 operates. The operation of relay M disconnects relay II from line if] and extends the connection from line I 0, through the inner front contacts of relay I l over conductors 2.3 and 24 and the upper brushes of switch 3-! to the windings of line relay 28 of the selected trunk OT. Relay II releases and relay 28 operates. Relay 28 closes a circuit for operating slow-to-release relay 29. Relay 29 connects ground to the lower terminal of set 21, thence through the lower brush of switch SI, conductor 25 and lowermost front contact of relay It to sleeve conductor II! to hold relay I4 operated and to hold the line-finder switch LF--I in usual manner. The release of relay iI causes the release of relay I2; but being slow in releasing relay Z does not open its lower front contact until after relay 25 has connected ground potential to conductor I9. The operation of relay 28 also closes a circuit for operating relay 3H. Relay closes a circuit for lighting the anii i) swering lamp 32 at the zero operators position and connects the ringing source (ii to the lower talking conductor of the trunk, an audible signal being thereby transmitted to the calling station to indicate that an operator is being signaled. When an operator answers the call by inserting a plug in answering jack 3%, relay 35 is operated through the sleeve of the plug. Relay 35 disconnects relay 28 thereby causing the release of relays 23 and 39, but relay 29 is held to ground at the front contact of relay 35. The answering erator then requests the calling subscriber to replace the receiver; if the call cannot thus be dismissed, a plug is inserted in the jack 3% to which trunk OT is connected at a trouble operators position thereby causing operation of relay 3'5. The zero operators cord is thereupon disconnected from jack 33 so that relay 35 releases and relays 28, 29 and 30 reoperate. Relay is? closes a circuit for operating relay 38 and relay locks under control of relay 29. With relay 3% operated, a circuit is closed for lighting lamp 59 at the trouble position. The plug may then be removed from jack 35 releasing relay 3 Since relay 38 is held operated under control of

relays

28 and 29, lamp 38 remains lighted and the out-of-order tone source til is connected to one of the talking conductor If then the calling subscriber replaces the receiver (or the trouble condition is removed), relay 2% releases thereby causing the release of relays 3i) and 38; and lamp 39 is extinguished. The release of relay 2Q disconnects ground potential from the sleeveterminal thereby causing the release of relay i of selector S-I and the return of the switches Si and LFl to normal in usual manner.

By means of the lamps such as S9 of the trunks in the group with OT, the trouble operator knows how many of the trunks in this group are being held on permanent signal calls; and, if this number of trunks leaves only enough trunks for use on zero operator calls, the key 58, associated 2 th primary finders having access to the first selectors to the banks of which this group of trunks is multipled, is operated thereby stopping the operation of these primary finders so that no more permanent signal calls can be antomatically extended to an operator. If a selector is seized and no dial impulses are received and the primary finder having access thereto has been stopped by operation of the key such as 58, the permanent signal alarm relay Ell is operated and an alarm actuated after an interval of from 20 to 40 minutes has elapsed.

What is claimed is:

1. In a telephone system comprising lines and selector switches and means for automatically connecting calling lines to said selectors, switching means for finding a selector to which a calling line is connected, and control means individual to said switching means, said control ieans rendered effective a predetermined interval of time following the finding of such a selector for automatically causing the selective operation of said selector.

2. In a telephone system comprising selectors and means for automatically connecting calling lines to said selectors, an impulse mechanism common to said selectors, finder switches for use in connecting said mechanism to any one of said selectors, means effective a predetermined interval of time after a calling line is connected to one of said selectors for completing the connection between said selector and said impulse mechanism, and means comprising said impulse mechanism and a stepping magnet of said selector for advancing the brushes of said selector to select a desired group of terminals in the bank of said selector.

3. In a telephone system comprising lines and selectors and means responsive to the origination of a call for extending the calling line to an idle one of said selectors, a finder switch, a plurality of said selectors being connected to terminals in the bank of said finder switch, means for advancing the brushes of said switch, means for stopping the advance of the finder switch as soon as its brushes encounter the terminals of a selector to which a calling line is connected and which has not yet been selectively operated, an impulse mechanism, means effective a predetermined interval of time after the advance of said switch is stopped for connecting said impulse mechanism to said selector, and means comprising said impulse mechanism and a stepping magnet of said selector for operating said selector to select a desired group of terminals in the bank of said selector.

4. In a telephone system comprising lines and selectors and means responsive to the origination of a call for extending the calling line to an idle one of said selectors, primary finder switches, a different group of said selectors being connected to terminals in the bank of each of said finder switches, means for advancing the brushes of said switches, means for stopping the advance of a finder switch when its brushes engage the terminals of a selector to which a calling line is connected and which has not been selectively operated, an impulse mechanism common to all of said finder switches, means operative a predetermined interval of time after the advance of one of said primary finders is stopped and comprising a master finder switch for connecting said impulse mechanism to the selector with whose terminals the brushes of said one of the primary finders are. in engagement, and means comprising said impulse mechanism and a stepping magnet of said selector for selectively operating said selector.

5. In a telephone system according to claim 2, means effective upon completion of said selective operation of the selector for disconnecting said impulse mechanism from the selector.

6. In a telephone system according to claim 3, means effective upon completion of said selective operation of the selector for disconnecting said impulse mechanism from the selector, the advance of said finder switch being thereupon resumed.

In a telephone system comprising lines and selectors and means for automatically connecting calling lines to selectors, primary finder switches each having a plurality of sets of brushes, each of said selectors being connected to terminals accessible to one of said sets of brushes, means for advancing the brushes of said finder switches, a control relay and a timing relay for each of said sets of brushes, means for stopping the advance of any one of said finder switches when one of its sets of brushes engages the terminals of a selector to which a calling line is connected and which is awaiting selective operation, said sto= 'ng means including the control relay of w reliever set of brushes engages the L als of such a selector, a master finder switch having a plurality of brushes, a contact on each of said timing relays i r connecting the associated brush of a primary finder switch to a different terminal accessible to one of the brushes of said master finder switch, means for starting the operation of said master finder switch whenever one of said control relays operates to stop the advance of a primary finder switch, said starting means including the timing relay associated with said one oi the control relays, means for stopping the operation of said master finder switch when one of its brushes engages the terminal to which the contact of said timing relay is connected, said stopping means including a relay individual to said one of the brushes of the master finder switch, an impulse mechanism, relay means individual to each of the brushes of said master finder switch for operatively and separately connecting said impulse mechanism to the brushes of the master finder switch, and means including said impulse mechanism, a brush of said master finder switch, the contact of one of said timing relays, a brush of a primary finder switch and the operating magnet of a selector which is awaiting selective operation for advancing the brushes of said selector to select a desired group of terminals.

8. In a telephone system comprising'lines and selectors and means for connecting calling lines to said selectors, an impulse mechanism common to said selectors, a finder switch for use in connecting said impulse mechanism to any one of a plurality of said selectors, means for advancing the brushes of said finder switch, means for stopping the advance of said finder switch when it engages the terminals of a selector to which a calling line is connected and which is awaiting selective operation, means effective within a predetermined interval of time after such a selector is found for completing the connection between said selector and said impulse mechanism, a group of trunks connected to one of the groups of terminals in the banks of each of said plurality of selectors, means comprising said impulse mechanism and an operating magnet of said selector for advancing the brushes of said selector to said group or" trunks, and means in said selector for automatically selecting an idle one of said trunks.

9. In a telephone system according to claim 8, a manual switchboard, an answering jack and a trouble jack at said switchboard, both of said jacks being connected to said selected trunk, an answering lamp and means effective upon seizure of said trunk for lighting said lamp, a trouble lamp, and means including said trouble jack for lighting said trouble lamp in place of said answering lamp.

10. In a telephone system. comprising lines and selectors and means responsive to the origination of a call for extending the calling line to an idle one of said selectors, a finder switch, a plurality of said selectors being connected to terminals in the bank of said finder switch, means for advancing the brushes of said switch, means for stopping the advance of the finder switch as soon as its brushes encounter the terminals of a selector to which a calling line is connected and which has not yet been selectively operated, an impulse mechanism, means effective a predetermined interval of time after the advance of said switch is stopped for completing a connection between said impulse mechanism and said selector, a manual switchboard, a group of trunks leading from the banks of said plurality of selectors to said switchboard, means comprising said impulse mechanism and a stepping magnet of said selector for operating said selector to select said group of trunks, and means for automatically operating said selector to seize an idle one of said trunks.

11. In a telephone system comprising lines and selectors and means responsive to the origination of a call for extending the calling line to an idle one of said selectors, primary finder switches, a dilferent group of said selectors being connected to terminals in the bank of each of said finder switches, means for advancing the brushes of said switches, means for stopping the advance of a finder switch when its brushes engage the terminals of a selector to which a calling line is connected and which has not been selectively operated, an impulse mechanism common to all of said finder switches, means operative a predeter mined interval of time after the advance of one of said primary finders is stopped and comprising a master finder switch for connecting said impulse mechanism to the selector with whose terminals the brushes of said one of the primary finders are in engagement, a manual switchboard, groups of trunks leading from. the banks of said selectors to said switchboard, the trunks in each of said groups being connected to the banks of the selectors in one or more of said groups of selectors, means comprising said impulse mechanism and a stepping magnet of said selector for operating said selector to select said group of trunks, and means for automatically operating said selector to seize an idle one of said trunks.

12. In a telephone system according to claim 2, keys, the operation of each key being effective to prevent the operation of one or more but not all of said finder switches.

13. In a telephone system according to claim 3, a key, and contact means controlled by said key for stopping the operation of said finder switch.

14. In a telephone system according to claim 8, a key, and contact means controlled by said key for stopping the operation of said finder switch.

15. In a telephone system according to claim 11, keys, one for each of said groups of trunks, and contact means controlled by each of said keys for preventing the operation of the finder switch or switches, having access to the selectors in whose banks the trunks of any group are connected.

16. In a telephone system comprising lines and selector switches and means for automatically connecting calling lines to said selectors, said selectors being controlled directly over calling lines, switching means for finding a selector to which a calling line is connected, and control means rendered effective a predetermined interval of time following the finding of such a selector for automatically causing the selective operation of said selector.

ROY M. BRAZELTON.