US1968420A

US1968420A - Telephone system

Info

Publication number: US1968420A
Application number: US657027A
Authority: US
Inventors: Albert C Powell
Original assignee: Bell Telephone Laboratories Inc
Current assignee: AT&T Corp
Priority date: 1933-02-16
Filing date: 1933-02-16
Publication date: 1934-07-31
Anticipated expiration: 1951-07-31

Description

J y 31, 9 A. c. POWELL 1,968,420

TELEPHONE SYSTEM Filed Feb. 16, 1935 11 Sheets-Sheet 2 GROUP REGISTER SEA/DER mu. ANNOUNCER 204 IN VEN TOR A. .c, POWELL July 31, 1934.

A. C. POWELL TELEPHONE SYSTEM Filed Feb. 16, 1933 11 sheets sheet 3 lNl/ENTOR A. C. POWELL ATTORNEY July 31, 1934. A. c. POWELL- 1,968,420

TELEPHONE SYSTEM Filed Feb. 16, 1953 11, Sheets-Sheet 4 INVENTOR A C. POWELL @aeam'w A TTORNEP July 31; 1934. A, Q POWELL 1,968,420

TELEPHONE SIISTEM Filed Feb. 16, 1935 1 ll Sheets-Sheet 5 FIG. 5

INVENTOR A. C. POWELL GPW ATTORNEY y 31, 93 A. c. POW EL| I 1,968,420

' TELEPHONE SYSTEM Filed Feb. 16, 1935 ll Sheets-Sheet 6 lNl/EN TOR A. C. POWELL By $6M ATTORNEY July 31, 1934; A. c. POWELL ,4

- I TELEPHONE SYSTEM Filed Feb. 16, 1933 ll Sheets-Sheet 7 10 mrsncspmva v CONTROL cmcu/r /Nl/ENTOR A. G. POWELL A TTORNEV A. c. POWELL' 1,968,420

TELEPHONE SYSTEM July 31', 1934.

Filed Feb. 16, 1933 ll Sheets-Sheet 8 N 3g INVENTOR m N m A. C. POWELL By I A77'ORNEY A. C. POWELL TELEPHONE SYSTEM Filed Feb. 1a, 1935 11 Sheets-Sheet 9 INVENTOR A. C. PUWELL By C A T TORNE V July 31, 1934. A. c. POWELL 1,953,420

TELEPHONE SYSTEM Filed Feb. 16, 1935 11 Sheets-Sheet 1o INVENTOR A. G. POWELL By 6. 4M

AT TORNEV July 31, 1934;,

FIG.

THOUSANDS A. C. POWELL TELEPHONE SYSTEM Filed Feb. 16, 1955 i1 Sheets-Sheet 11 HUNDREDS lNl/EN TOR A. C. POWELL BY 6 6M 4 TTORNEY Patented July "31, T934 TELEPHONE SYSTEM Albert C. Powell, New York, N. Y., assignor to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Application February 16, 1933, Serial No. 657,027

29 Claims.

manner, during periods when the trafiic is light the number of calls incoming at certain positions may be insufiicient to Warrant the services of an individual operator and a single operator may have'to handle calls incoming from a number ,of different types of oflices.

It is also desirable to reduce the amount of work that the operator has to perform in completing a connection. Accordingly, the operator has been provided with equipment for automatically connecting her head set with the trunks over which I calls are incoming and for preparing circuits for automatically ringing the called subscriber under control of keys common to the trunks of her position. In addition this equipment is arranged to identify the nature of the incoming trunks and reacts thereto to cause the transmission of the called line number either automatically or orally.

In accordance with the present invention, an improvedtrunk circuit is provided, in which the operation of a common ringing key operates a relay which locks under the control of the calling subscriber and releases to display a disconnect signal. In addition a control circuit is provided which will identify trunks of four difierent kinds and if an incoming trunk is one over which called line numbers are transmitted by means of code impulses, it transfers the trunk conductors to a recorder, provides a holding circuit for the trunk until the impulses have been received at which time the original holding circuit is reestablished, prevents the transmission of a signal to initiate the transmission of impulses if the trunk plug is still in the jack from a previous call, and renders the common ringing keys inefiective if the pulses are not completely recorded. 7

This position circuit is also equipped for handling calls incoming from other manual ofiices or from dial ofiices equipped with call announcer machines. It the position equipped with sucha control circuit is grouped with a position having no recorder for receiving the call indicator im-- pulses, all calls must be handled from the former (c1. ua-27) position. Means have therefore been provided to connect a continuous tone to the operator's telephone if under such a grouping arrangement she attaches her telephone to the wrong position.

This and other features'of theinvention will be moreclearly understood from a consideration of the following description in connection with the drawings in which:

Fig. 1 shows in diagrammatic form a panel dial office and a portion of a trunk outgoing'to a manual office; t

Fig. 2 shows in diagrammaticform a panel tandem ofiice equipped with call announcer mechanism and a portion of a trunk outgoing to a manual ofiice;

Fig. 3 shows a manual oflice and a portion of a trunk outgoing to a second manual ofiice;

Fig. 4 shows a complete trunk circuit at the manual office; I

' Fig. 5 shows a portion of a trunk circuit appearing at a manual oifice;

Figs. 6 and 7 show a trunk splitting circuit;

Figs. 8 and 9 show a position control circuit; and

Figs. 10 and 11 show a call indicator recorder."

The portion of the trunk circuit shown on Fig. 5 is the same for each of the three'types of trunks but has been shown only once. Figs. 1 and 5 show a complete trunk incoming from a panel oiiice equipped with a call indicator inc-- pulser which will be referred to hereinafter as a call indicator trunk.

Figs. 2 and 5 together show a complete trunk incoming from a panel ofiice equipped with a call-announcer mechanism which will be'referred to as a call announcer trunk. Although the ofiice equipped withthe call announcer has been shown as a tandem oflice, it might equally well be an originating ofiice similarly equ pped.

Figs. 3 and 5 together show a complete trunk connecting two manual offices which will be identified as a straightforward trunk.

Fig. 4 with the exception of the skeletonized incoming circuit is a copy of Fig. 3 of Patent No. 1,905,662, granted to H. M. Ulrich April 25, 1933. This trunk circuit difiers in certain details from the trunk s of Figs. 1 to 3 and is normally served by the position control circuit disclosed'in the above identified application. However, it may also be served by the position control circuit 'of; the present'applicationr The equipment at the' manual ofiice' includes the trunk circuits of the four types shown 'in Figs. 1,2; 3 and 4 whichmay all appear before a single operator or may appear in individual" positions. Assuming that there are a number of positions, each operators position is provided with a trunk splitting or grouping circuit as shown in Figs. 6 and 7 and a position control circuit as shown in Figs. 8 and 9. For positions at which call indicator trunk circuits appear, a recorder such as shown in Figs. 10 and 11 is provided.

Other positions may or may not have such a recorder. The trunks appearing at an operators position are divided into two groups and each group is connected in multiple to the splitting or grouping circuit. One group is also connected in multiple directly to the position control circuit, while the other group is connected thereto over the back contacts of the splitting relays. In addition each trunk is provided with a pair of sequence relays which determine the order in which the trunks may be connected to the position control circuit.

The splitting circuit of Figs. 6 and '7 has for its purpose to permit the establishment of operators divisions of desirable size. Key 725 controls the relays of group 600 and key Z26 con trols the relays of group 610. When none of the splitting keys is operated the control circuit is connected through the splitting circuit to all of the trunks at the switchboard. The operation of key 725 upon operating the relays of group 600, opens the conductors between the positions and disconnects all of the trunks at the left. The operation, by key 726, of the relays of group 610 disconnects the trunks of the right group from the trunks of the left group and from the control circuit which normally serves them. Since each position normally serves forty trunks, it is therefore possible to form operators positions containing forty or more trunks in multiples of twenty. Since the group of trunks at the right of the position is not directly connected to a control circuit, the operating circuit for the splitting relays has been carried over the back contact of the adjacent splitting keys to prevent creating a group of trunks to which no control circuit has access. For example, the circuit of the splitting relay of the left adjacent position corresponding to relay 711, which operates all of the remaining splitting relays of the group, extends over the operated contact of key 724 of the left adjacent position, normal contact of key 725, normal contact of the emergency relay 936 to ground over conductor Z29 which extends over the back contact of the emergency relays of other positions to ground. The circuits of relays 701 and 711 are modified by the use of straps 730 and 731 where they appear at the right or left end positions, respectively. For the purpose of describing the action of the trunk and control circuit, it will be assumed that key 725 has been operated, operating relay Z01 over strap 730, the

, operated contact of key 125, inner lower normal similar key and relays at the next right position 'circuit by inserting plug 801 in jack 802 thereby closing a circuit from ground through the rightwinding of repeating coil 803 through the plug and jack contacts and the transmitter 800 to battery through the winding of relay 8%.

Call indicator call The first call to be described will be one over a call indicator trunk. When the subscriber at substation 100 desires to call a subscriber in the office at which the equipment under consideration is located, he will remove his receiver from the switchhook whereupon his line will be connected by means of line finder 101 to district selector 102 and the sender 103. He will then dial the number of the wanted subscriber and the sender 103 will control the district selector 102 and the ofiice selector 105 to select the trunk outgoing to the wanted omce.

After the trunk has been selected, the sender connects a relay across the tip and ring conductors, establishing a circuit from battery through the upper winding of relay 110, upon left winding of repeating coil 111, upper back contacts of relays 11 1 and 115 overthe tip brushes of the office selector 105 and the district selector 102 through the relay (not shown) the sender, back over the ring brushes of the district and office selectors, lower back contacts of relays 115 and 11%, lower left winding of repeating coil 111 to the lower winding of relay 110 and ground. Relay 110 operates, closing a circuit for relay 518. Relay 518 closes a circuit from battery through lamp 509, resistance 507,

lower back contact of relay 506 to ground at the outer upper front contact of relay 518, ligh ing the trunk guard lamp as an indication that a call is incoming on the associated trunk. It also connects battery over its inner upper contact to conductor 520, preparing a circuit for

relays

501, 112, etc. In addition, it closes a circuit from ground over its lower front contact, upper back contact of relay 510 to the winding of relay 620, and at its upper back contact it removes ground from a circuit for controlling a group busy register.

Relays

620 and 621 constitute a pair of sequence relays individual to the trunk and the circuits for these relays extend in series over the contacts of the corresponding relays of other trunks in the first group and over the contacts of the splitting relays 612 and 613, to the se quence relays of the second group so that the trunks of the entire position are served in a 1.

The circuit of relay particular arbitrary order. 620 extends over the back contact of relays corresponding to relay 621, over the back contact of relay 622, upper back contact of relay 613 and thence to battery over the front contact of a relay corresponding to relay 603 at the position on the right. Assuming that no other trunk is associated with the control circuit of Figs. 8 and 9, relay 620 will operate, in turn closing a circuit from battery through the wind- 1:

ing of relay 621, upper front contact of relay 620, over the front contact of relay 602, conductor 631, through the winding of relay 935 to ground at the back contact of relay 934.

-With

relays

620 and 621 operated the operators position is trunk.

Relay 621 in operating closesa circuitfrom battery through lamp 632, outer lower front con-J tact. "of relay 621, conductor 633, inner lower front contact of relay 808, winding of relay 927,

to groundat the lower back contact of relay. 913.. Relay 927 operates in series with lamp 632, and closes acircuit from battery over the back contact of relay 908, through the winding of relay'910, upper front-contact. of relay 927,. lower'back contact of relay 921, conductor 630,.

inner lower. front contact of relay 621, conductor 521, through resistance 507, back contact of relay 506 to ground at the upper front relay. 910 closes an obvious circuit for relay 909,- which in turn closes a circuit for relay 908.

Relay 909 connects battery over its upper front contact in shunt of the winding of relay 910 over the front contact of relay 927 to conductor.

630. The connection of battery to the winding of relay 910 releases that relay and the connection of low resistance battery to conductor 630 reduces the current flow in lamp 509 sufliciently to dim that lamp. As soon as relay 910 releases, it in turn releases relays 909 and 908 ;,so that battery is removed from the winding of relay 910 and conductor 630, permitting the lamp to return to full brilliance and relay 910 to .reoperate. This cycle of operations is continued until ground is removed from conductor 630 by the operation of relay 506 as described hereinafter.

With

relays

620 and 621 operated, a circuit is closed for

relays

501 and 112 which extends from battery over the inner upper front contact of relay 518,.conductor 520, upper winding of relay 501 in parallel with the winding of relay 112, conductor 522, upper front contact of relay 621, lower front contact of relay 620, conductor 634, inner upper front contact of relay 808, resistance 906, back contact of relay 905 to ground at the upper back contact of relay 912. Relay 501 closes a locking circuit for itself and for relay 112 over the inner upper front contact of relay 501, conductor 523, lowermost front contact of relay 808,

. throughthe winding of relay 835 to ground at the back contact of relay 825. Relay 835 in operating closes a circuit for relay 912 which removes ground from the operating circuit of re lays 501 and 112 to prevent the connection of 1 any other trunk to the control circuit. It also disconnects battery from the emergency operating circuit for relay 501 which will be described hereinafter. Relay 912 at its upper front contact, closes a circuit for relay 916, and at its lower front contact, closes a. circuit through the winding of relay 915. Relay 915 looks over its inner upper front contact, lower back contact of relay 903 to ground at the outer lower front contact of relay 919. Relay 915 closes-a circuit from ground over its upper front contact, back contact of relay 913, winding of relay 904 and battery. Relay 904 in turn operates relay 905, further disconnecting ground from the operating circuit of relay 501. a

When relay 112 operates, the position circuit makes a test to determine whether or not the. plug 508 is still in the jack with which it waslast used@ When the plug 508 is in a jack,zre-' lay 506 is operated, but with the plug removed,

"relay 506 is not operated and groundis c1osd.:-..

individualized "to this particular ing of relay 822 which operates.

' and 818.

over itsinner lower back contact, outer upper and each type identifies itself to the control cir-' cuit. A call indicator trunk of the type. being described is identified by the connection of battery through relay 115 over the middle upper front contact of relay. 112 to conductor 120. Therefore, as soon as relay 112 operates, a circuit is closed from conductor 120 over the upper front contact of relay 901, lower back contact of relay 809, normal contact of relay 832, back contact of relay 1051 in the recorder circuit, winding of relay 814 to ground. Relay 115 cannotoperate in series with relay 814, but relay 814 operates to identify the trunk as a call indicator trunk, and, in conjunction with other relays, prepares the position to handle a call indicator call. Relay 814 also opens the circuit of relay 826 to prevent the premature generation of the order tones.

lay 916 closes a circuit from battery through the upper winding of relay 815, front contact of relay 814, conductor 947 to ground at the outer upper contact of relay 916. its outer lower front contact, over the upper front contact of relay 821 to grounded conductor 947. It also extendsits locking ground to the wind- In addition, relay 815 closes a circuit from ground at its inner upper front contact over the upper back contact of relay 903 to the winding of relay 828 and battery. Relay 828 in turn operates relays 819 The function of these relays will be described hereinafter.

Relay 822 in operating closes a circuit from ground over its innermost upper contact through the winding of relay 1052 to battery toprepare the recorder circuit for receiving the call indicator impulses. Relay 1052 in operating connects ground to conductor 1060 thereby supplying locking ground for the register relays. It also connects ground to the winding of relay 814 in shunt of battery, thereby releasing relay 814,

and back over the circuit of relay 814 to the windtrunk conductors from it. Relay 829 locks to ground at its front contact thus holding operated under the control of the trunk.

With relay 814 operated, the operation ofre- Relay 815 looks over Relay 822 in operating also closes a circuit from a extending from the tip conductor over the upper battery through the-winding of relay 807, back" The operation of relay 807 front contact of relay 115, conductor 533, outer upper front contact of relay 808, upper front contact of relay 807, lower back contact of relay 1024, through the windings of

relays

1003, 1002, and 1001 in series, outer upper back contact of relay 1024, front contacts of

relays

807, 808, conductor 534, lower front contact of relay 115, to the ring conductor.

With relay 821 operated, the operation of relay 916 starts the generation of the order tones by closing a circuit from ground over the outer upper front contact of relay 916, conductor 94'? to the upper front contact of relay 821 and thence over the lower normal contact of relay 838 to the upper winding of relay 826 and battery and over the upper normal contact of relay 838 to the winding of relay 839 and battery. Relay 839 performs no function in connection with call indicator trunks. Relay 826 in operating connects the right winding of tone coil 82? over its inner front contacts, through condensers 84'? and 848 to the left winding of the operators repeating coil 803. It also closes a circuit from the source of tone through the left winding of repeating coil 82?, inner lower back contact of relay 913, back contact of relay 836 to ground at the middle lower front contact of relay 826, thereby completing the circuit for transmitting the first order tone. In addition, relay 826 operates relay 836 in a circuit extending from battery through the winding of relay 836, back contact of relay 902, outer lower front contact of relay 826, to ground at the inner upper front contact of relay 916. Relay 836, in operating, disconnects ground from the left winding of tone coil 82?, interrupting the tone, and connects ground over its inner upper contact to the winding of relay 837. Relay 837 reconnects ground to tone coil 82'? and closes a circuit from battery through the winding of relay 838, lower contact of relay 837, front contact of relay 821 to grounded conductor 947. Relay 838 opens the circuit of relay 839 and of relay 826 thereby disconnecting the tone coil from the operators headset and in turn releasing relays 836 and 83?, thereby removing ground from the primary winding of tone coil 827. Relay 838 looks over its inner lower front contact to ground over the front contact of relay 821 and conductor 947.

Relays

836, 837 and 838 are slow to operate thereby determining the periods for which the tone is applied and the interval between tones. Relay 838 also closes a circuit from battery through the upper winding of relay 805, upper front contact of relay 838, front contact of relay 821 to grounded conductor 947, thereby operating relay 805. Relay 805 normally connects the operators telephone to the tip and ring conductors of the trunk but, since relay 807 is operated, this is ineifective at the present time. The operation of

relays

826, 836, 837, 838 and 805 serves to transmit a warning tone to the operator although it is not transmitted out over the trunk.

The substitution of the circuit through

relays

1001, 1002 and 1003 for battery and ground through relay 110 as previously described causes the release of the relay in the sender to initiate the transmission of the call indicator impulses. These impulses are received on

relays

1001, 1002 and 1003, relay 1003 responding to negative impulses, relay 1002 to positive impulses and relay 1001 to heavy impulses of either polarity although the code does not include heavy positive impulses except as a final pulse. The first time that relay 1003 operates it closes a circuit from grounded conductor 1060 over the front contact of relay 1003, inner upper back contact of reia 1024, lower back contact of relay 1004, winding of relay 1005, lower winding of relay 1004 to battery. Relay 1005 operates in this circuit closing a circuit from battery through the lower winding of relay 1004, winding of relay 1005, upper winding of relay 1004, front contact of relay 1005 to grounded conductor 1060. The upper operating winding of relay 1004 is maintained shunted at this time over the operating circuit of relay 1005. When the pulse ends this shunting ground is removed and relay 1004 operates. The next operation of relay 1003, therefore, closes a circuit from grounded conductor 1060 over the front contact of relay 1003, inner upper back contact of relay 1024, lower front contact of relay 1004, through the lower winding of relay 1004 to battery, holding relay 1004 operated and shunting the winding of relay 1005 so that relay 1005 now releases. At the termination of the second pulse, relay 1004 also releases.

As is well known, the call indicator code consists of two negative impulses which may be either light or heavy so that

relays

1004 and 1005 operate and release as each digit is received. A light positive pulse may be transmitted either before the first negative impulse or between the two negative impulses and this positive impulse and the heavy negative impulses serve to operate the registers. The first time that relay 1004 operates a circuit is closed from battery through relay 1010,

upper back contact of relay 1020, upper front contact of relay 1004 to grounded conductor 1060. When relay 1004 releases at the termination of the digit, the locking circuit closed by relay 1010, which extends from battery through the winding of relay 1010, winding of relay 1020, inner lower front contact of relay 1010 to grounded conductor 1060, becomes effective and relay 1020 operates. At each operation of relay 1004 one pair of the transfer relays is operated, relays 1010 and 1020 being operated during the reception of the first or stations digit, relays 1011 and 1021 following the thousands digit, relays 1012 and 1022 following the hundreds digit, relays 1013 and 1023 following the tens digit, and relays 1014 and 1024 following the units digit. Each of the five registers consists of four relays which may be numbered from left to right 1, 2, 3 and 4. During the first or stations digit, 2. positive impulse before the first negative impulse closes a circuit from grounded conductor 1060 over the front contact of relay 1002, back contact of relay 1005 which has not yet operated, back contact of relay 1010 which is also non-operated through the lower winding of relay 1031, while a positive impulse between the two negative pulses after the operation of relay 1005 closes a circuit from grounded conductor 1060 over the front contact of relay 1002, front contact of relay 1005, lower back contact of relay 1020 through the lower winding of relay 1033 to battery. Marginal relay 1001 which responds to heavy negative impulses, if operated during the first negative pulse closes a circuit from grounded conductor 1060 over the front contact of relay 1001, back contact of relay 1004, since relay 1004 does not operate until the termination of the first negative pulse, lower back contact of relay 1010, through the lower winding of relay 1032 to battery, while, if operated during the second negative pulse, it closes a circuit over the front contact of relay 1004, inner lower back contact of relay 1020 to the lower winding of relay 1034' and battery. Similar circuits may be traced under the control of the other transfer relays to the other registers.

tive pulse of the last or units digit, relay. 1014 is operated closing a locking circuit through relay 1024 to grounded conductor 1060 which becomes effective after the last negative impulse has been received. Relay 1024 in operating rearranges the impulsing circuit so that the negative relay 1003 may respond to the final heavy positive pulse. For this purpose the circrit extends from the tip conductor, as previously traced, to the upper front contact of relay 807, thence over the lower front contact of relay 1024, through the winding of relay 1003, upper front contact of relay 1024, lower front contact of relay 807, back to the ring conductor instead of in series through the windings of the three relays. Relay 1024 also connects resistance 1061 in parallel with the winding of relay 1003 to protect it. Since relay 1024 is now operated, the operation of relay 1003 connects ground. from conductor 1060 over the front contact of relay 1003, inner upper front contact of relay 1024, through the winding of relay 1053 to battery. Relay 1053 closes a locking circuit for itself through the winding of relay 1051 to ground at the lower front contact of relay 1014. When the final heavy positive pulse is terminated, relay 1003 releases and relay 1051 operates, disconnecting ground from the winding of relay 115 to permit that relay to release and restore the tip and ring conductors to the windings of relay 110. It also connects ground over its upper front contact to the lower winding of relay 820 which looks over its inner upper front contact to ground at the middle lower front contact of relay 915 as a signal that the designation has been completely received. The restorationof the circuit for relay 110 causes that relay to reclose the holding circuit for relay5l8 and connects ground in shLmt of the winding of relay 829 which thereupon releases.

The operator may now depress one of the ringing keys 940, 9 11, 9&2 or 943 to establish the proper ringing control for calling the wanted subscriber. Assuming that she operates key 943, a circuit is closed from ground over that key J through the winding of relay 933, upper front contact of relay 820, inner lower front contact of'relay 821 to battery. With relay 933 operated, ground from key 943 is extended over the inner lower contact of relay 933, inner lower back contact of relay 921, conductor 948,middle upper front contact of relay 501 to the winding of relay 511 and battery. A circuit is also closed from the contact of key 943, over the upper armature and outer upper front contact of relay 933, outer lower back contact of relay 920, over conductor 949, middle lower front contact of relay 501 through the winding of relay 513 and battery.

A third circuit is closed from key 943 over the lower contacts and lower armature of relay 933,

outer upper back contact of relay 920, inner lower front contact of relay 901, winding of relay 903 to battery. Relay 903 looks over its inner lower front contact to ground at theouter upper front contact of relay 915. It also closes a circuit from ground at the middle lower contact of relay 916,

inner upper front contact of relay 903, outer lower contact of relay 821, inner upper back contact of relay 813, lower front contact of relay 822 to battery through the winding of register 842 which records the number of calls handled over call indicator trunks. The operation of relay 903 also opens the circuit of relay 828 which in turn releases relays 819 and 818. It likewise closes a circuit from ground at the upper front contact of I v .from the trunk.

relay 815. over theouter. upper front contact of relay-903 to battery through the winding of relay 832. -'Ihe functions of these relays willbe described hereinafter. Relay 903 alsoconnects ground over the lower contact of relay 919,over the lower front contact of relay 903 to the looking circuit for

relays

820 and 821 to prevent battery from being disconnectedfrom the common ringing keys and the release key. Furthermore, relay 903 opens the locking circuit-of relay 915. 1

An additional circuit is closed from ground on key 9&3 over the lower contacts and armature of relay 933, upper armature and both upper contacts of relay 933, winding of relay 911 and battery. Relay 911 in operating closes ground over its outer upper front contact, over the lower front contact of relay 820, providing the recorder circuit has been completely operated, inner upper back contact of relay 920, conductor 950, inner upper front contact of relay 112 to-the winding of relay 510 and battery. Relay 510locks over its inner: .upper front contact to ground at the lower front contact of relay 518. Relay 911 connects ground over its two upper contacts, upper back contact of relay 923, inner upper back contact of relay 921, conductor 951, inner lower front contactof relay 501, through the winding of relay 516 and battery. In addition relay 911 connects ground .over its two upper contacts and inner lower front contact to the winding of'relay 922 and battery. Relay 922, in operating, connects ground over its 'lower front contact, innerlower back contact of relay'920, inner lower front contact of relay 919, through the winding of relay 817 and battery. Relay 817, if either relay 818.0r 829 has released, connects ground from the back contact of that relay over the front contact of relay 817 to the winding of relay 825 and battery. Relay 825 disconnects ground from the windingof relay 835 thereby opening the locking circuit of relay 501 and relay 112 so that the positioncontrol circuit is now completely disconnected from the trunk circuit; 1

Relay 835 in releasing opens the circuit of relay 912 which in turn .opens the operating circuit of relays 915 and 910. Relay 915v releases, if its locking circuit has'been opened by relay 903, in turn opening the locking circuit of relay 903. In additionrelay 9l5'releasesrelay 904 which in turn' releases relay. 905. Therefore after an interval measured by the slow releasing character of relays 904 and 905, ground over the upper'back contact of relay 912 is connected .to the operating circuit of relay 501 and battery over the lower back contact of relay 912 to the emergency circuit .for'op'erating relay 501 so that another trunk may be connected to the control circuit. Relay 916 immediately removes the ground from conductor 947 releasing relays 805, 838,815 and 822. It also opens the'operating circuit'for the peg count meter. The release of the ringing key releases relays 911, 922, 817 .and 825 and opens the operating circuit of relay 903. Relay 993 in releasing opens the holding circuits of

relays

820 and 821 whereupon the position control circuit is completely restored to normal.

In the trunk circuit, relay 516 looks over its inner lower front contact, lower back contact of relay 515 to ground at the outer upper front contact of relay 518. With relay 516 operated; a

holding circuit is closed for relays 513 and 511 over their outer lower front contacts and the outer upper front contact of relay 516, to ground at the front contact of relay 518, to prevent their release when the control circuit is disconnected 1 winding of the repeating coil 804 to ground. Assuming that the subscribers line is idle and no click occurs, the operator then inserts plug 508 in the subscribers jack whereupon ground on the sleeve of the jack completes a circuit for the sleeve relay 506 which operates. Relay 506 in operating completes the tip conductor and disconnects the busy test circuit. It also connects ground over its inner upper front contact, lower front contact of relay 516, to the winding of relay 503, and its inner upper normal contact, upper front contact of relay 511 to interrupter 512 and battery. When the interrupter closes its contact, relay 503 operates, locking over its inner upper front contact to battery at the inner upper front contact of relay 518. With relay 503 operated the tip conductor is extended over the outer upper front contact of relay 503 and the inner lower front contact of relay 511, winding of the tripping relay 515, inner lower front contact of relay 513 to negative superimposed ringing current source 514, while the ring conductor is extended over the lower front contact of relay 503, inner upper front contact of relay 511 to ground. Relay 511 therefore determines to which conductor the ringing current is to be connected while relay 513 determines whether positive or negative superimposed current is to be employed.

The called subscriber is signaled in this circuit and when he removes his receiver from the switchhook, relay 515 is energized, opening the locking circuit for relay 516 which thereupon releases in turn releasing relays 511 and 513. The release of relay 511 also opens the circuit of relay 503 which in turn releases relay 515 and the circuit is now ready for conversation. While relay 515 is operated it connects ground over its front contact to an alarm circuit to guard against its failing to release and thereby preventing ringing the next subscriber. The restoration of the tip and ring conductors, by the release of relay 503, permits supervisory relay 113 to operate in series with the called subscribers line thereby closing a circuit from battery through the winding of relay 114, front contact of relay 113 to ground at the inner lower front contact of relay 510 which is held looked under the control of relay 518. The operation of relay 114 reverses the connection of battery and ground through the windings of relay to the incoming trunk conductors to cause a supervisory signal to be given to the district selector 102 for charging purposes.

When the called subscriber restores his receiver at the end of the conversation, relay 113 is released and in turn releases relay 114, signaling the district selector that conversation has been terminated. The district selector may also receive this information from the calling subscriber and release after an interval. The release of the district selector opens the circuit of relay 110 which opens the holding circuit for relay 518 thereby in turn releasing relay 510. With relay 510 released, a circuit is closed from ground at the back contact of relay 510, over the lower front contact of relay 506, resistance 507, to lamp 509 causing that lamp to light steadily as a disconnect signal, as long as the plug remains in the jack. When the operator removes the plug from the jack, relay 506 releases, extinguishing lamp 509.

If this trunk should be reselected before the Call announcer call Trunks incoming from tandem offices where. the connection is to be completed through the operation of a call announcer are made up of the portion shown on Fig. 2 and the same portion shown on Fig. 5 as is used in connection with the call indicator trunk. These trunks are identi-l. fled to the control circuit by the connection of battery through the winding of relay 21 i, inner lower front contact of relay 212, conductor 216, middle upper front contact of relay 901, upper back contact of relay 809, through the winding. of relay 812 to ground at the upper back contact of relay 813. Relay 812 in operating opens the operating circuit of relay 826 which controls the order tone relays to prevent the order tone signal from being transmitted to the operator prema turely. When relay 916 operates in response to the connection of the trunk with the position control circuit in the manner previously described, relays 811 and 806 are operated over the front contacts of relay 812 and the back contact of the call indicator relay 814. Relay 811 in operating locks through its lower winding and lower front contact, normal contact of relay 813, front contact of relay 821, which operates if the plug 508 is not in a jack as described, to grounded conductor 947. Relay 810 is also operated over the locking circuit of relay 811. Relay 806 in operating disconnects the tip and ring conductors of the trunk from the operators headset to prevent clicks from being transmitted to the telephone 115 circuit when the trunk reversing relay operates and releases to signal the sender. It also connects the tip and ring conductors together at its front contacts to charge condenser 849 before connecting the operators telephone to the trunk.

Relay 810 closes a shunt around the winding of relay 812 which now releases. This shunt reduces the resistance in series with relay 214 which now operates and reverses the tip and ring conductors to the sender, thereby preparing for the operation of the call announcer 204.. At the same time relay 810 connects ground from conductor 9 17 over its lower front contact, to the lower winding of relay 806 to hold it operated after relay 812 releases. Relay 812 in releasing connects ground from conductor 947 over the lower back contacts of relays 81 1 and 812, lower normal contact of relay 838 to the upper winding of relay 826 and battery. Relay 826 causes the successive operation of

relays

836, 837, 838 and 805 in the man- 195 ner previously described, thereby transmitting an order tone to the operator whose headset is connected to the control circuit.

The order tone relays in this case are also used to time the duration of the interval during which ground is connected to relay 214, that is the duration of the signal to the sender. The operation of relay 810 simultaneously operates relays 214 and 826, and in parallel with relay 826, relay 839. When relay 838 operates it terminates the second 45 tone impulse and operates relay 805. It also opens the operating circuit of relay 839 which releases slowly to extend the time during which relay 214 is held operated slightly beyond the last tone. When it completely releases, it closes a 150 circuit from battery through the winding of relay 813, upper front contact of relay 811, back contact of relay 839, upper front contact of relay 838, front contact of relay 821 to grounded conductor 947. Relay 813 on operating looks over its lower front contact and the back contacts of relays 812 and 814 or the front contact of relay 821 to grounded conductor 947 and disconnects ground from .the upper armature of relay 810 thereby releasing relay 214 to terminate the reverse battery signal and start the transmission of the call announcement. In addition relay 813 releases relays 811 and 810 and prepares the circuit for the call announcer peg count meter 830. The release of relay 810 in turn releases relay 806 removing the short circuit from the condenser 849 and connecting the tip and ring conductors through to the armatures of relay 805 which now being operated extends them through the left winding of the operators talking coil 803 so that the "operator may receive the wanted number from the call announcer.- Relay 810 is slow to release and slightly delays the release of relay 806 until the reversing relay in the trunk has had time to release in order to prevent an objectionable click from being received by the operator.

The completion of the call takes place as described for the call indicator trunk. When the ringing key is operated, in turn operating relay 903, a circuitis closed from .battery through the winding of peg count meter 830, inner upper front contact of relay 813, outer lower front contact of relay 821, inner upper front contact of relay 903 'toground at the middle lower front contact of relay 915, thereby recording on meter 830 the completion of a'call over a-call announcer trunk.

Straightforward call Trunks incoming from manual OlTlCBS, com- .monly known as straightforward trunks are made 7 in the jack 302 of the outgoing trunk. In this case battery and ground are supplied from the cord and. the circuit extends through the two windings of relay 310 in series and the windingof supervisory relay 304 of the operators cord.

, However, the lower winding of relay 310 is of such high resistance that supervisory relay 304 can not .lay 518, which is a slow-to-release relay for straightforward trunks, and the connection of the trunk with the position control circuit proceeds as previously described. A straightforward trunk is identified to the control circuit by the absence of potential on

conductors

216 and 120 and therefore neither relay 814 nor relay 812 is operated. In consequence, neither relay 806 nor relay 807 is operated to prevent the transmission of the tone to the calling operator and the order tones are audible to both operators. Since neither relay 814 nor relay 812 is operated, the order tones are not delayed, and relay 826 operates in a circuit through its upper winding, lower back contact of relay 838,'back contact of relay 812, back contact of relay 814 togrounded conductor 947, without waiting for the test by relay .at the originating ofiioe.

821 to determine whether or not the plug has been Withdrawn. The tones and wantednumber may therefore be transferred from one operator to the. other, but the battery for the operation of any of the ringing relays, such as relays930, 931, 932 is not available until relay 821 has operated indicating that the plug has been removed from the multiple. Likewise, since neither relay 822 nor relay 813 is operated, the operation of the ringing key followed by the operation of relay 903 completes the circuit for register 831 over the lower back contact of relay 822, inner upper back contact of relay 813, lower front contact of relay 821, inner upper front contact of relay 903 to ground at the middle lower front contact of relay 916 to record the completion of a connection over a straightforward trunk.

This control equipment may also be used in connection with the'older type of automatic listening common key ringing trunk such as shown in the patent to H. W. Ulrich above mentioned and shown completely in Fig. 4. The sequence relaysimilar to relay 621 individual to this trunk carries an extra pair of contacts which connect conductors 404 and 405 together. This type of trunk is identified'to the position circuit by the connection of battery from the lower back contact of relay 411, through to the right winding of relay 415, middle lower front contact of relay '419 to conductor 444, over the outer lower front contact of relay 917 through the winding of relay 824 to ground. Relay 415 does not operate in this circuit, but relay 824 in operating connects ground over its lower front contact through'the lower winding of relay 821 to battery, operating that relay which looks and prepares the ringing 1 and release keys as previously described. It is to be noted that with the plug 430 in the jack 431, relay 410 is operated and connects ground over ;its inner upper front contact to the winding of relay 411 which receives battery over the back contact of relay 403 when the trunk is released Relay 411 locks from battery over its outer lower front contact, through the winding of relay 411 to ground at the front contact of relay 410 therefore preventing the connection of battery to the winding of relay 415 as long as the plug 430 remains in a jack. The

operation of relay 824 therefore both identifies the type of trunk and acts as a test of whether or not the plug is in a jack. The operation of one of-the ringing keys, in turn operating relays 922 and 911, connects ground over the inner up,- per contact of relay 911, back contact of relay 923, upper contact of relay 922, outer upper back contact of relay 921, to conductor 444 in shunt of the winding of relay 824, operating relay 415. Relay 415 looks through its left winding over the front contact of relay 403 and the back contact of the tripping relay 433. the trunk from the control circuit and prepares the trunk for ringing the wanted subscriber. Otherwise, the operation of the control circuit is the same as for-the previously described straightforward trunk.

In case a call comes in over a straightforward trunk which must be connected to the intercepting operator, after the intercepting operator has determined the correct routing, she will be connected under the control of a pair of sequence relays similar to

relays

620 and 621 to the position control circuit. 'The intercepting operator then passes the correct number to the trunk op erator whereupon the operator depresses key 502 to reconnect the trunk with the position and Relay 4 15 releases then disconnects plug 508 from the jack leading to the intercepting operators position. When the trunk is disconnected from the intercepting jack, the position control circuit releases from the intercepting position and when relay 506 releases with key 502 operated, a circuit is completed from ground at the upper front contact of relay 518, lower back contact of relay 506, the lower winding of relay 501, key 502, conductor 952, middle upper front contact of relay 917, through the lower winding of relay 90'], lower back contact of relay 90 1, lower back contact of relay 912 to battery. Relay 90? operates looking over its upper contact to the operating circuit of relay 912 which is closed when relays 501 and 312 lock. Relay 907 prevents the flashing relays 908 to 910 from functioning. From this point the operation is the same as previously described. Key 502 may also be used for emergency operation in case of failure of the sequence relay chain circuit.

If a call comes in over a trunk which is either a call announcer or call indicator trunk as shown in Figs. 1 and 2, requiring the services of an intercepting operator, and is then reconnected to the trunking operators position, it is necessary for the control circuit to recognize that the trunk has been previously connected for the same call in order to prevent the control circuit from functioning the trunk to signal the sender in the panel office to transmit a called number. This feature is accomplished by the use of relay 309. When the trunk was connected with the intercepting jack,

the position was released from the trunk by the operation of trunk release key 925, operating relay 91]. which in turn operated relay 510 in the trunk circuit. Relay 510 locks under the control of relay 518 as previously described. When the control circuit is reconnected with the trunk, relay 809 is connected in a circuit from battery through its lower winding, middle lower front contact of relay 917, lower back contact of relay 911, inner upper back contact of relay 920 to conductor 950, which extends over the inner upper contact of relay 212, for example, to the winding of relay 510 and over the locking circuit of that relay to ground at the lower front contact of relay 518. Since relay 911 is operated, before relay 510 is operated on an ordinary call, relay 809 can not operate, but when the position circuit is connected with a trunk on which relay 510 has already been operated, relay 809 operates locking through its upper winding and inner upper contact to ground at the outer lower contact of relay 915. With relay 809 oper-- ated, the circuit of

relays

814 and 115 is opened as well as the circuit of relays 812 and 214 and, therefore, the control circuit is prevented from sending a signal to the sender. When relay 911 is operated as a result of operating one of the ringing keys, relay 809 is disconnected from the circuit of relay 510 and when the control circuit releases, the locking circuit of relay 809 is opened.

When a call is abandoned after the trunk has been connected to the position control circuit, relay 310, for example, releases in turn releasing relay 518. The release of relay 518 disconnects battery from the winding of relay 501 thereby opening the locking circuit of that relay and in turn opening the circuit of relay 835. Relay 835 in turn releases relay 912 and the position control circuit is restored to normal in the usual manner with one exception. Relay 915 remains looked over the back contact of relay 903 to ground at the lower front contact of relay 919. With relay 915 operated and relays 912 and 903 released, a circuit is closed from battery through the winding of relay 913, upper back contact of relay 912, inner lower front contact of relay 915, back contact of relay 903 to ground at the lower front contact of relay 919. Relay 913 in operating closes a circuit from ground at the outer upper front contact of relay 915, outer upper front contact of relay 913 to the inding of relay 905 holding that relay operated. It also closes a circuit from ground at its outer lower frontcontact, through the lower winding of relay 821 holding that relay operated. lnzaddition, it closes a circuit from ground at its inner upper front contact through the lower winding of relay 826 to battery. With

relays

826 and 913 operated, a circuit is closed through the primary winding of tone coil 827, through resistance 914, back contact of relay 835 to ground at the middle lower front contact of relay 826 thereby creating a tone in the right winding of relay 826 which is transmitted over the

condensers

847 and 843 to the left winding of the operators repeating coil 803. This tone is reduced in volume due to the introduction of resistance 91 1 in the circuit. In ad dition relay 913 disconnects ground from the winding of relay 92? thereby disabling the flashing relays and preventing the flashing of the guard lamp of any trunk. With relay 905 held operated, the operating circuit for relay 501 is also opened, preventing the connection of another trunk with the position control circuit. The reduced steady tone created by the joint operation of

relays

913 and 826 is a signal to the operator that the call is abandoned. She will therefore operate release key 925 which in turn operates relay 923 in a circuit from ground over key 925, winding of relay 923, outer lower front contact of relay 918 to battery at the lower front contact of relay 821. Relay 923 connects ground from key 925 over its outer lower front contact; upper back contact of relay 920, inner lower front contact of relay 901 to the winding of relay 903 and battery. Relay 903 looks over its inner lower front contact to ground at the front contact of relay 915. Relay 923 also connects ground over its inner lower front contact to the winding of relay 911 which performs its usual functions. in the release of the control circuit. In addition it connects ground over its upper front contact, lower back contact of relay 921, conductor 9 18, middle upper front contact of relay 501 to the winding of relay 511 and battery. Relay 511 is ineffective at this time, since none of the other ringing relays is operated. Relay 903 in operating opens the holding circuit of relay 915 and that relay releases, in turn releasing relay 913. Relay 913 in releasing opens the circuit of relay 825 which terminates the abandoned call tone. It also reconnects ground to the winding of relay 927 permitting the flashing circuit to function if a call is incoming at the time.

It also releases relay 905 thereby preparing a circuit for connecting "runks with the position control circuit and in addition closes the shunt at its lower back contact around resistance 91a so that the order tones may be of the normal strength.

On call indicator calls, once the call has been extended to the trunk, the abandonment of the call by the calling subscriber is ineffective to release the connection, but is ehective to change the wanted number to a series of zeros. If,-due to some error in the functioning of the circuit, the pulsing is incomplete, no abandoned call signal will be given. Since the pulsing is not completed, the ground from the lower front contact of relay 1052 remains connected in shunt of the winding of relay Sl land in series with the winding of relay 115 holding the trunk connected to the recorder and preventing the trunk relay from releasing to transfer the trunk conductors from the position control circuit back to the line relay of the trunk. The trunk therefore cannot recognize that the call has met with difiiculty. However, as long as this condition continues no other trunk can be connected to the position control circuit until the operator recognizes the condition and releases the position by operating the release key.

The position control circuit hasseveral other special functions in connection with call indicator trunks. For example, it is arranged to create a delay before disconnecting the trunk in order to allow enough time for the district selector circuit in the dial office to advance and complete a circuit over the trunk for the line relay 110, before the holding circuit for r lay 518 is opened at the position control circuit. For this purpose, when relay 815 operates following the association of a call indicator trunk with the position control circuit, it closes a circuit from battery through the winding of relay 828, upper back contact of relay 903 to ground at the inner upper front contact of relay 815. Relay 828 closes an obvious circuit for relay 819 which in turn operates relays 818. Relay .818 disconnects ground from the armature of relay 817. When one of the ringing keys or the release key is operated, in turn operating relay 903, the circuit of relay 828 is opened and relay 828 starts to release, and in turn releases relays 819 and 818. All three of these relays are slow-to-release relays and intro-.

duce an average delay of. approximately one second before relay 818 again closes ground to the.

armature of relay 817 thereby permitting the operation .of relay 825, the release of relay 835 and the disconnection of the trunk from the control circuit. If relay 110 is reoperated promptly by the advance of. the district selector, the reoperation of relay 110 shunts the winding of relay 829 and causes that relay to release connecting ground to the armature of relay 817 over the back contact of relay 829 and cance ing the balance of the time delay.

When for any reason the recorder circuit is not satisfied by the sender, resulting in a partial or no display of the called number, relay 820 is not operated and ground is not removed from the winding of relay 115 by the completion of the call indicator pulses. The common ringing keys having been made ineffective by the operation of relay 815 and key 925 having been made partially ineiiective by the operation of relay 822, as already explained, the non operation of relay 820 permits the keys to remain in this condition, this is to prevent the operator from releasing the trunk by a common ringing key and thereby setting the trunk for ringing without knowing the called number or to release the trunk by the release key and thereby lock out the trunk leaving the calling subscriber to abandon the call. Since ground remains connected to relay 115, the tip and ring conductors of the trunk circuit remain connected to the control circuit. In the case of such a partial or no display condition, the operator is instructed to operate key 841 and challong-e on the trunk and if the calling party is present to obtain the desired number and com-- plete the call. The operation of key 841 closes a circuit for relay 816 over the front contact of relay 822, relay 816 looking over its lower contact to ground at the outer lower front contact of relay 915. In operating, it connects battery and ground through the windings of coil 823 to the tip andring conductors leading to the trunk to hold the connection. It also releases relay 807 thereby connecting the trunk through to the operators repeating coil. After the number is obtained from the calling party the operator will make the common keys eifective by operating key 840 which closes a local operating circuit for relay 820, relay 820 locking under the control of relay 915. Relay 820 closes the circuits for rendering the ringing and release keys effective which were opened by the operation of relays 815 and 822. The operation of a ringing key or the release key will then cause the circuit to function as already described, with the exception that the operation of relay 903 closes a circuit from ground over the inner upper front contact of relay 815, outer upper front contact of relay 903, winding of relay 832 and battery. Relay 832 connects resistance 833 and condenser 834 around coil 823 to protect the contacts of relay 115 and then opens the energizing circuit for relay 115 so that this relay releases reestablishing the circuit for relay 110 over the trunk. When the position control circuit returns to normal, releasing relay 915, relay 816 is released.

Several emergency features are also provided. If for any reason the sequence relays 620 and 621 fail to function properly to automatically connect the associated trunks to the common equipment, the sequence emergency key 623 may be operated closing a circuit from ground at the front contact of relay 8% over key 623, through the winding of relay 622 to battery. Relay 622 opens the battery and ground supplies for the sequence relays and therefore suspends their operation,.as well as releasing all operated sequence relays. Key 623 is a locking key and therefore, following its operation, the trunks are connected to the control circuit only by the operation of individual trunk keys such as key 502. With this operation the flashing circuit does not function and the trunk guard lamp retains a steady light while the trunk is connected to the common equipment.

Assuming that the position control circuit of Figs. 8 and 9 is serving trunks at two physical positions, for example the position indicated by the splitting circuit of Figs. 6 and 7 and the similar circuit to the left of it, if the position control circuit should fail to function properly, or the recorder circuit of Figs. 10 and 11 fail, the position emergency key 924 would be operated. Key 92 i operates relay 921 which in turn operates relay 920 and relay 936 which is associated with the splitting circuit of Figs. 6 and 7. Re-

lay 936 in turn releases relays 84:4, 901, 917 and 918 and 808. The operation of relays 920, 921 and 93% opens all the conductors between the control circuit and the associated splitting circuit thus isolating the control circuit that is in trouble. The operation of relay 936 with strap 730 connected and strap 731 open closes a circuit over its middle lower front contact for relay 701. Relay 701 in turn operates relays 703 and 604 and these relays in turn operate relays 704, 702, 60.1, 602, and 603 thereby preventing the associa-- tion of the trunks of this position with the control circuit of the position at the left which has been assumed to be unequipped with a call indicator recorder. For an intermediate position, which is wired with strap 730 open and strap 731 closed, the operation of relay 936 would cause the operation of relay 711 and the corresponding splitting relays of setv 610, thereby splitting half