US1531006A - Telephone system - Google Patents

Description

March 24, 1925.

E. E. HINRI'CHSEN TELEPHONE SYSTEM 4 Sheets-Sheet 1 In veq'ior: [award E. Hmn'c/zsen March 24, 1925.

E. E HINRICHSEN TELEPHONE sY sTEM' 4 Sheets-Sheet 2 b E 1?. new/2 my.

E. E. HINRICHSEN TELEPHNE s'Ys TEM 4' Sheets-Sheet 5 March 24, 1925. 1,531,006

E. E. HINRICHSEN TELEPHONE SYS TEM Fil Jan. l3, 1921 4 $heets-$heet 4 Ta a Patented Mar. 24, 1925.

1,531.,Qtt

UNITED STATES PATENTOFFICE.

EDWARD E. HINRICHSEN, or NEW YORK, N. ASSIGNOR To WESTERN ELECTRIC COMPANY, INCORPORATED, on NEW YORK, N. Y. ACORPORATION on NEW YORK.

T LEPHONE SYsTEM.

Application filed January 13, 1921. Serial No. 436,884.

To all whom it may concern Be it known that I. EDWARD E. HINRIOH sEN, a citizen of the United States,residing at New York, in the county of New York,

State of New York. have invented certain new and useful Improvements in Telephone Systems. of which the following is a full, clear, concise, and exact. description.

This application relates to telephone systems and particularly to machine switching systems of the type in which relay mechanisms are employed for interconnecting the calling and called subscribers.

it feature of the invention is a new method for controlling the change-over from one brush to another by the direction switch employed for piloting the connec-' tions.

Another feature of the invention resides in the use of a direction switch by the attendant subscriber in place of the individual line selecting keys heretofore used in systems of this nature. By the use of such a direc tion switch the complete operation of this 5 system is made more uniform and the num' ber of devices under the control of the attendant operator is greatly reduced.

Another feature of the invention is a means whereby the attendant operator may set up a connection to a busy line and leave it in such a condition that the line will be automatically seized when the busy condition is removed.

Another feature of the invention is a new 5 arrangement for signalling the central office when the battery supply for the system fails. The drawings comprise a diagrammatic representation of a preferred means for carrying out the invent-ion. There are four figures which, when placed together, Figure 2 below Figure 1, Figure 3to the right of Figure 2 and Figure 4; above Figure 3 and to the right of Figure 1, form a complete circuit diagram. Figure 1 contains a representation of two groups or subscribers lines together with the necessary relays for connecting said lines to acentral ottice trunk line; Figure 2 shows the means for connecting the said lines to a link circuit, and a link circuit to the said lines; Figure 3 Shows a link circuit together with severalauxiliary circuit-s such as the ringing circuit, the busy tonecircuitand the buzzer circuit; and Figure 4 shows a' central office trunk line.

In the drawings, a system of about eighty lines capacity is represented. A call'from one station to another is made bydialing the number of thecalled station. An originating call to the central office is made by dialing the central office code which connects the calling station to the central'oiiice so thatthe subscriber may give thedesired number to the operator thereat. The disconnect signal is given to the central oflice when the calling subscriber hangs up. The calling subscriber can also flash the operator' by manipulating hisswitchhook in the'lusual manner.

An incoming call is received by the attendant subscriberand may be extended to any desired station by the operation of her calling dial. The supervisory relay at the central office is operated as soon as the attendant answers the call and remains operated until the called station has answered and hung upagain or until the attendant subscriber operates a disconnect key incase the call is not extended to a station. A disconnect signal is given to the central oiiice automatically when the called subscriber hangs up at the end of the conversation but provision is made for the called subscriber to signal the attendant if desired.

Calls to the central oflice may be 0rigi nated by the attendant and extended to any desired station.

The link circuits to be usediin establishing local connections are notused on central office connections. 5 Each trunk is provided with apparatus for connecting directly to any line and whena calling subscriber dials the central *oflice code the link circuit to which he was originally connected functions to select an idle trunk and connects it to his line and then releases ready for use on another connection.

Provision isma'de for preventing any line from calling the central office directly. Incoming calls may, however, be completed to such lines.

The circuit arrangements are such that the connection links are used in. rotation. A linkhaving once been selected remains busy to incoming calls until all the other link circuits have been used even though it has been released in the mean time.

If the link circuit-selected by anincoming call fails to pick up the calling line the call is transferred after a brief interval to'the nate a call to the central oflice thus avoiding double connections. t, a

The detailed operation of the individual circuits shown on the drawing is as follows:

Line circuit.

TWhen a subscriber such as. 111 originates a call,.a line relay such as 200 operates in series with his telephone set controlling the operation of other relays which causes an idle link circuit to connect to the line. As soon as the connection has been made the sleeve conductor of the calling line is grounded in the link circuit making theline busy to any link circuits or trunks which may select it and operates cut-offrelay 201 which releases the line relay 200; When the line is released at the endof the connection the removal of the ground from the sleeve conductor releases the cut-off relay and leaves the line free to be called.

Group circuit and c-mergcncysmrt circuit.

When the relay 200 operates it causes the operation of group relayt202 through a circuit from ground, front contact and left hand armature of relay 200, Winding of relay 202 to battery and ground Relay 202 in attracting its armatures establishes a con necti on from ground, inner right hand armature and back contact of relay 203, outer right hand armature and front contact of relay 202, conductor 20st, left hand armature and back contact ofrelay300,conductor- 301, armature and back contact of relay 205, left hand armature and back contact of relay 206, Winding of relay 207 to battery and ground. Relay 207 becomes energized in this circuit and then locks up in a circuit including conductor 301, the winding of relay 205; the right hand armature and front contact of relay 207, the

winding of relay 207 to battery and ground. Circuits are thereupon established for relays 2-08, and 209. The circuit for relay 208 extends from grounded battery, the winding.

of relay 208, the nextto the outermost left hand armature and front contact of .relay 207, the front contact and inner right hand armature or relay 202, the'back conr tact and inner right hand armature of relay 203 to ground. tends from grounded battery, the Winding of relay 209, the innermost left hand armature'and'contact of relay 207, the front con- A circuit for relay 209 ex-- tact and right hand armature of ,relay 200, t-lie:,. front contact and .left hand arn'ia-ture of relay 202, the back contact and left hand armature ,of relay 203 to ground.

Through the action ,of relays 208 and 209, the calling line is extended to the link circuit of .Figure 3, whereupon the calling supervisory relay 302 is operated by the closed loop of the calling subscribers line. Relay 302 closes a circuit from ground, the Winding of relay .303the left hand armature and front contact of relay 302, right hand armature and backv contact of relay 304,

winding of relay 305 to battery and ground. Relay :305 attracts its armatures and places aground on conductor 306 to which relays 208 and209 lock. "The ground on conductor 306 is alsoi fextended through the contacts of relays209 and'208yto the sleeve conduc- 1elea se of relay 307 a circuit is established from ground on conductor 204 through the armature'and front, contact of relay 308, the back contact and right hand armature of relay 307, the outermost right hand armature and back contact of-rela-y 300, the winding of relay.309, the back contact and innernrost right ,hand armature of relay 000 to battery and ground, whereupon relay 3300 becomes energized. WVhen this ground is removed by the subsequent release of relav 308, relay 309 remains locked up through the winding of relay 300 which thereupon operates. This circuit is as follows: ground on conductor 2041-, left hand Winding of relay 300, inner left-hand armature and front contact of relay 309, Winding of relay 309 back contact and inner right hand armature of relay .300 to battery and ground. As soon asrelay 300 operates the circuit is as follows: ground on conductor 204-, the left hand Winding of relay 300, inner left hand armature and front contact of relay 309, Winding of relay 309, right hand winding of relay 300 to battery and grourul.

l.he'cycle of operations of relays 307 and 308 is repeated and on the next release of relay 307, relay 309 is short-circuit and released, relay 300 being held up until relay 308 releases. This momentarily opens the start lead30l and closes an emergency lead which advances the selection to the next link circuit. When this condition is established there will be a circuit from ground on conductor 204, the left hand armature and front contact of relay 300, back contact and outer left hand armature of relay 309, emergency lead 310, left hand ari'nature and back contact of relay 210, right hand winding of relay 206 to battery and ground. llela becomes energized and extends condu 301 to conductor 211 leading to a left hand armature of a relay 212 individual to the next link circuit and performing the same functions as relay 206. Thus when a call is initiated it must be picked up by the first idle link circuit very quickly or the emergency circuit will operate to make eii' ective the next idle link circuit.

L mic circuit.

set of finder relays, a set of connecting relays and the apparatus for controlling the opera-' tions of the finder and connecting relays supplying transmitter current and testing and ringing the called lines.

lVhen a station originates a call, the operation of a group relay such as 202 operates a relay such as 207 through the back contact of the allotter relay such as 206. The operation of relay 207 connects the relays such as 209 to the contacts of the line relays and connects the relays such as 208 to the contacts of the group relays such as 202. This causes the operation of the relay 208 corresponding to the group of ten lines in which the calling line is located and relay 209 corresponding to its position in the group. This connects, the talking circuit to the calling supervisory relay 302 individual to the link circuit, which operates, operating in turn the holding relay 305. Relay 305 when operated closes a locking circuit for relays 208 and 209 and supplies ground for operating the cut-off relay 201 for the calling line and operating the allotter relay 206.

Assuming that the link circuit, whose operation is being described, is any other than. the last, relay 206 looks up through its right hand winding and contact, the winding of relay 210 and the back contact of relay 213 of the last link circuit, this circuit being as follows: ground, armature and back contact of relay 213, front contact and right hand armature of relay 206, winding ofrelay 210, right hand winding of relay 206, to battery and ground. y

The operating circuit of relay 207 is opened by the operation of relay 206, but relay 207 is locked up through relay 205 which operates and prevents the operation of relay 200 from operating the relay corresponding to relay 207 of the neXt link circuit. Relay 205 which is common to all the links releases upon the release of relay 202 of the groupv cuit. When the last link circuit isselected and its relay 21 loperates, it locks up through its right hand Winding and contact and winding of relay 21 i and contacts of the corresponding relays of all other link cir cuits in series. telay 213, of the last link operating, opens the locking circuit for relays corresponding to 206 and 210 in all the other link circuits, releasing relayscorresponding to 200 of such link circuits as are not in actual use. The release of relayscorresponding to relay 210 in any other of the link circuitsreleases relay 213 of the last link circuit and reestabli shes the locking circuits for the relays corresponding to 206. In case of trouble in a link circuit which prevents relays corresponding to relay 206 from. operating in the normal manner within a predetermined time, the actionof the emergency start circuit grounds the emergency start lead 310 which operates relay 200 through its right hand windingand at the same time opens the regular start lead 301 and releases relays 207 and 205. As soon s the action of the ei'i'iergency circuit removes the ground from the emergency start lead relay 210 operates and relay 2120f the next link is operated.

When the holding relay 305 operates it closes the operating circuit for relay 3l2.

Relay 312, however, does not operate since it is short-circuited by a contact of the supervisory relay 202. When the subscriber operatesl'iis dial, relay 302 releases in responseto each interruption of the line circuit by the dial springs, permitting relay 312 to operate. The operating circuit for relay 312 is then as follows: grounded battery, resistance 314i, winding of relay 312,

back contact and inner right hand armature of relay 313, conductor 306, trout contact and right hand armatureof relay 305 to ground. Relay 312, in operating, operates magnet 315 which steps the direction switch 1 ahead. Magnet 315 controls an extra armature which closes a contact to operate magnet 316. The armature of magnet 315 which controls its contacts is slow in releasing, so

thatit does not fall back on a'momentary release of relay 312, although the other armature follows the impulses received from relay 312 and steps the switch. ahead. Magnet 316, when it operates, permits the holding pawl of the switch to engage with its ratchet so that the switch does not release so long as nn'ignet 316 is energized. When the dial comes "to rest relay 302 remains operated and relay 312 is released long enough to permit both armatures of magnet 315 to release. Magnet 316 is slow to release so that it remains operated momentarily after the release of relay 315, grounding the group brush 317 and operating the connecting relay associated with the group of ten lines in which the called line is located We will asleading to relay 215.- In this manner relay 215 will become operated. The original operating circuit of relay is opened on the release of nmgnet- 316 but relay 215 remains operated in series with relay 319 which itself becomes energized. This circuit is as follows: ground on conductor 306, winding of relay 319, conductor 320, right hand armature and front contact of relay 215, winding of relay 215 to battery and ground. The release of magnet 316 removes the pawl from engagement with its ratchet and permits the direction switch to return to normal.

l lelays and 312 and magnets and 316 function in the same manner responsive to the second operation of the dial but as relay 319 is now operated. magnet 316 in operating, energizes relay 321 in a circuit extending from ground, right hand armature and front contact of magnet 310, innermost right hand armature and front con-- (act of relay 319, winding of relay 321 to battery and ground. When magnet 310 releases after the dial comes to rest the units brush is grounded, operating the units relay corresponding to the position of the called line in its group. In accordance with our assumption this unit series of impulses consists of a single interruption of the calling line circuit and brush 322 comes to rest on its first contact and grounds conductor 323 operating thereby units relay 216.

Assuming the called line. 191 to be bus-1; and the cut-off relay 2-47 to be operated by ground on the sleeve 2&8 of the called line. then upon the operation of relays 215 and 216 a circuit will be established from ground on the sleeve 2418 of the called line through the corresponding contacts of relays 215 and 210 to the sleeve conductor 32a of the link circuit through the left hand armature and front contactof relay 321, the normal contacts of the inner left hand armature of relay 313, the winding of relay 313 to battery and ground. Relay 313 operates and locks up to ground on conductor 306 in turn locking up relay 321 in a circuit from battery, winding of relay 321, front contact and armatureof relay 321, front contact and innermost right hand armature of relay 313 to ground on conductor 306. Relay 313 also opens the circuit ofrelay 312 to prevent the direction switch from responding to any further movement of the dial and connects busy tone through the condenser 326 to the calling subscriber. The path of the busy tone is as follows: from conductor 327, leading from a sourceof busy tone through the front contact and outermost left hand arm ature of relay 313, conductor 323, back con-- tact and outermost right hand armature of relay 325, condenser 326, right hand winding of relay 329 to battery, whence by 111- ductance in the windings of relay 329 busy magnet- 330 to battery and ground. Magnet 1 330 attracts its armature and automatically interrupts its circuit. This causes a rapid automatic vibration of the armature of magnet 330 which so effects the potential'on conductor 32'? that a tone is set up thereon.

Assuming the called line to be idle, relay 313 does not operate because battery connected to its winding is opposed by battery connected tothewinding of cut-on relay 247. Upon the release of magnet 310, relay 321 becomes deenergized. This connects the slee 'e 324- through a back contact of relay to a winding of supervisory relay 329 which becomes operated and causes the operation of relay 313. A circuit for the energization of relay 329 is as follows: from grounded battery, the winding of cut-ofli' relay 24:7, sleeve conductor 2 18, through the corresponding contacts of relays 215 and 216, conductor 324, left hand armature and back contact of relay 321, normal contact of the innermost right hand armature of relay 325, left hand winding. of relay 329 to ground. Relay 329 inattracting its armature extends the ground on conductor 300 through its contact and armature to the normal contacts of the innermostleft hand armature of relay 313, the winding of relay 313 to battery and, ground. Relay 313 becomes energized and locks up in the circuit previously traced.

Since relay 321 is deenergized at this time a circuit will be established for relay 325, said circuit extending from grounded battery,

winding of relay 325, back contact and right.

hand. armature of relay 321, front contact and innermost right hand armature of relay 313 to ground on conductor 306. Relay 325 transfers the sleeve conductor 3 1 from the left hand winding of relay 329 to a ground connection on conductor 306. Relay 325 also connects the tip and ring of the called line to the armatures of ringing relay 331.

Interrupted ringing current is now supplied to the called line from the source of such ringing current shown in the right ture of relay 331, front contact and innermost left hand armature ofrelay 325 through contacts of relays 216 and 215 over the loop of the called substation 191, back through the contacts of relays'215 and216,

the outermost left hand armature and front:

vof the receiver at the called substation.

Thereupon relay attracts its armatures and locks itself in a circuit including its right hand winding, its front contact and innermost right hand armature to ground on conductor 306. Through itsleft hand armatures it extends the called line to con trol of the called supervisory relay 329. Talking current is supplied to the called line through the windings of relay 329, and to the calling line through the windings of relay 302. The connection is now in a stable condition and conversation may now be carried on. l

At the end of the conversation the re lease of the apparatus is effected by the calling station replacing its receiver and causing the deenergization of relay 302. Relay 302 iii-retracting its armatures releases its control over the holding relay 305 and when after an interval this relay becomes released, all of the relays under its control return to normal and the connection is restored.

In case the trunk code is dialed, relay 304 becomes operated in place of one of the relays corresponding to relay 215 and relay 304 looks up in a circuit including battery, its winding, its front contact and innermost left hand armature and the front contact holding relay 305 togroundJ The trunk relay 304 opens the operating circuit of the holding relay 305 and connects ground froin the front contact of relay 302 to a relay in the first idle trunk circuit. circuit extends from ground, winding of relay 303, left hand'armature and front contact of relay 302, right hand armature and front contact of relay 304, conductor 334, innermost left hand armature and back contact of relay 400, winding of relay to battery and ground and in parallel therewith through the back contact and outermost right hand armature of relay 400 to the winding of holding relay 401 to batterv and ground.

Upon the operation of relay 304, a circuit is established for the operation of relav 335 asfollows: ground, fourth arina-V t tre of the set of left hand armatures of relay 208 individual to line 111, outermost left hand armature and front contact of relay 209, conductor 217, outermost left and left hand armature of the This hand armature and front contact of relay 304, left hand winding of relay 335', back contact and armature of relay 336to b'attcry and ground. Relay becomes energized and extends the ground on conductor 217 through. its outermost left hand armature, conductor 337, outermost right hand armature and front contact of relay 208, conductor 218, armature 101 of relay 100 and front contact co-operating with said armature, winding of relay 102 to battery and ground causing the energization of said relay 102. Acircuit is also established-from ground on conductor 217 through the innermost left hand armature and front con tact of relay 335, conductor 338, outermost right hand armature and front contact of relay 209, conductor 219, innermost left hand armature and front contact of relay 100, winding of relay 103 to battery and ground causing the energization of said rela v 103. Relay 335 also completes'a circuit from ground on conductor 311, right hand armature and front contact of relay 335, right hand winding of relay 335, Wind ing of relay 336 to battery and ground; whereby relay 336 is energized to open the original energizingcircuit of relay Relay 335 is individual to the link circuit but relay 336 is common to all link circuits so that when relay 336 operates it prevents the operation of any other relay corresponding to relay 335 until the one here shown becomes deenergized. it

The operation of relays 102 and 103 extends the calling line to the trunk shown in Figure 4. Relay 102 is then looked up in a circuit from ground, the right hand armature and front contact of relay 401, contacts 402 of key 403, back contact and outermost right hand armature of relay 404, conductor 405, front contact and armature of relay 102, winding of relay-102 to battery and ground. Relay 103 isalso locked up in a circuit including ground, right hand armature and front contact of relay 401, contacts 402 of key 403, conductor 406, front contact and armature of relay 103, winding of relay 103 to battery and ground. Ground was also extended from conductor 406, 'through the right hand armature and front contact of relay 100, conductor 104, right hand winding of relay 407 to battery and ground. Relay 407 locks up through its front contact and innermost right hand'armature to ground on conductor 406. p r

Relay 401 also places ground on conductor 408 for a purpose which will appear hereafter. The busy lam 409 is illuminatedin response to the energization of relay 401.

Relay 400 is short-eircuited through its own back contacts and by the ground on'conduc-' tor334'and will not become energized until relay 302 releases, It will be remembered 428 in operating opens the circuit of relay 413- i As soon as the call has been amnvorcd by an operator, relay -32 operatesin a circuit including grouinl, the tip conductor of the trunk at the central office, contacts 423 of lie 424, contacts 434 of key 430, right and left hand windings of relay 432 in. series, contacts of l-zey 424. ring conductor of the trunk at the central oi'lico to grounded battery. Relay 432 in operatingcauses the operation of relay 436. The rela? 4336 con i'iects relay 437 in a circuit which may be traced from grounded battery, Windingof relay 437, contacts 433 of lrcy 430, front contact and outermost left hand armature of relay 423, left hand rinature and front contact of relay 436 to ground. Relay 43".- in operating extends the calling line to the central oiiice. Relay 420 is cut off and dermergized but relay 401 is held operated by the outermost left hand arn'iature and front contact ofrelay 437,. whereupon relay 439 operates in series with the calling line and in turn causes the operation of relay 440. Relay 440 opens the circuit of relay 432 and places a non-inductive shunt 441 across the Winding of the supervisory relay 439. Relay 436 is maintained operated by relay 439. The connection is now in a stable condition and the subscriber may converse with the operator at the central ofi'ice.

lVhen the subscriber hangs up, relays 439 and 440 release permitting relay 432 to operate which prevents the release of relay 436. The high resistance of relay 432 releases the supervisory relay at the central office. As soon as the disconnection. takes place at the central office, relay 432 releases,

releasing relay 436. This releases relay 437' which in turn releases relay 401 and then in turn releases the reinainii'ig operated relays of the circuit. i

If the operator should disconnect before the subscriber hangs up, relays 439 and 440 release, but relay 432 does not operate and relay 436 releases. This releases relay 43? and permits relay 420 to operate. This holds up relay 401 and grounds the tip side of the line operating the line relay again at the central office and relighting' the line lamp. When the operator restores the connection;

relays 432, 420 releases.

436, and 4.37 operate and relay Incoming calls.

Then an operator plugs into a trunk Wl'tli a cord circuit, relay 432 operates, operating ates and locks up, lighting the line lamp 442.

innermost left hand armature of relay 422,

normal contacts of the innermost left hand armature-of relay 444, conductor 445, right hand armature and front contact of relay. 436 to ground. Rela-y 433 looks up in a circuit including battery and ground, its left hand Winding, its left hand armature and front contact to ground over the circuit just traced. The attendant subscriber at station 490 answers by means of the listening key 446, operating thereby relay 422 whichrelea'sos relay 433 and extinguishes v line lamp 442. The circuit for relay 422 may be traced from grounded battery, winding of relay 422, contacts 447 of key 446 to; ground. Guard lamp 448 lights as it is in multiple with the Winding of relay 422. Ree

lay 439 operates, operating relay 440 Which bridges the non-inductive shunt 441 across the Winding of relay 439. Retardation coil 449 Was bridged across the line in series with the low resistance Winding of relay 432'by the operation of relay 422 and a short-circuit isremoved from its middle high resistance Winding by the operation of relay 440. Relay 432 may release but relay 436 is held operatedby contacts of relay 439.

To extend the'call to a station, the attendant subscriber operates the station key which comprises the left hand contacts of key 430. This opens the circuit of relay 428 and operates relay 105. The circuit for rclay=105 may be traced from grounded bat tery, winding of relay 105, conductor 106, normal contacts of the inner right hand armature of relay 416, contacts 450 of key 430, contacts 451 ofkey 446 to ground. Relay 105 connects the trunk to thecommon selecting apparatus and operates relay 404 in a circuit including grounded battery, Winding of relay 404, conductor 452 innermost right hand armature and front contact of a relay 105' to ground. Relay 404 When operating transfers the attendant suhscribers' telephoneset to the other, side of the contacts of relay 43'? thereby operating relay 420. Relays 439 and. 440 release, but relay 422 remains operated. The release of relay 440' short-circuits the high resistance Winding of the retardation coil 449 andrelay 432 operates and prevents the release of relay 436. Relay 401 operates and. closes an operating circuit for relay 107 which however is short-circuited at this time so that it does not operate. The circuit for causing this may be traced from the top side of relay 107 through contacts 108 of relay 105, conductor 109 front contact and innermost right hand armature of relay 422, right hand armature and front contact of relay 420 to ground and from the lower terminal of relay 107 to contacts 112 of relay 105, conductor 408, to ground on the left hand armature of relay 401.

The attendant subscriber now operates her dial to select the desired number and relay 420 releases at each interruption of the circuit by the dial springs, permitting relay 107'to operate. llelay 107 in operating, op crates stepping magnet 113 of the switch which steps the wiper ahead. carries an extra armature which controls a contact which. operates magnet 114. Magnet 114 in operating allows the holding pawl of the switch to engage with its ratchet and closes a circut through its innermost right hand armature and front contact and the back contact of relay 115 to group brush 116. The armature of'ina-gnet 113 which operates the contacts is sluggish so that it does not release when relay 107 is momentarily re leased in response to the dial impulses although the other armature follows the impulses received from relay 107 and advances the switch to the operating position. When the dial comes to rest, relay 107, is released long enough to permit both arlnatures of magnet 1 13'to release. Magnet 114 is sluggish so that it remains operated momentarily so that the group brush 116 is grounded, operating the connecting relay associated with the group often lines containing the called line. i

Wewill assume that a call is being set up to the subscriber at station 110; therefore the set of impulses for moving the group brush 116 consists of a single interruption of the attendant subscribers line circuit and group brush 116 comes to rest on its first contact.

Uponthe release of magnet 113, conductor.

117 is grounded, causing the operation of relay 102. The circuit for the energization of relay 102 may be traced from ground, the armature and back contact of magnet 113,

the innermost right hand armature and front contact of magnet 114, the left hand armature and back contact of relay 115 group brush 116, conductor 117, contacts 118 of relay 105, winding of relay 102 to battery and ground. Relay 102 looks up toground on conductor 405, which ground is supplied from the left hand armature and front contact of relay 401, conductor .408, contacts 112 of relay 105, winding of relay 115, contacts 119 of relay 105, to conductor 405. Relay 115 is operated in this circuit. In a short interval magnet 114 retracts its armatures Magnet 113' and permits the switch to return to normal. Relays 420, 107 and magnets 113 and 114 function in the same i'uanucr in response to the second operation of the dial but as the relay 115 is now operated the operation of magnet 11 i. operates relay 410 in a circuit including grounded battery relay 410, condin-tor outeru'iost right hand armature and front contact of relay 105 front contact and outermost right hand armature of magnet 114, front contact and right hand armature of relay 115 to ground. When magnet 113 releases it grounds the units brush 120, operating the units relay corresponding to the position in its group of the called line.

In accordance with our assumption, this last series of impulses consists of ten interruptions of the attendant subscribers line. This causes the units brush 120 to come to rest on its tenth contact and ground conductor 121 whereupon relay 122 is operated. The circuit for the operation ofrelay 122 may be traced as follows: grounded battery, relay 122, contacts 123 of relay 105, conductor 121, units brush 120, front contact and left hand. armature of relay 115, front contact and inner right hand armature of magnet 114,

back contact of magnet 113 to ground. Re-' 122, sleeve conductor 413, left hand armature and front contact ofrelay 410, normal contacts of the inner left hand armature of relay 416. contacts 417 of key 403. winding of relay 416 to battery and ground.

If the line is busy the sleeve is grounded so that relay 416 operates and locks up, in turn locking up relay 410. The operation of relay 416 also releases relay 105. leaving relay 107 directly under control of the station key comprising the left hand contacts of key 430. The release of relay 105 opens the holding circuit for relay 102, but the ground connection for locking up relay 102 is now furnished by the operation of relay 416.

In case the line is not busy, relay 416 does not operate and relay 410 releases upon the releaseof magnet 114 connecting the sleeve through the resistance 411 and relay 412 to ground. Relay 412 operates in series with the cut-off relay of the line and locks up through relay 416 which opcrates, cutting off and releasing relay 105. As relay 410 is now normal and relay 412 is operated, the operation of relay'416 operates relay 414 which cuts the sleeve of plied to the called line through the; back contact and left hand winding of relay 407. Direct current is supplied to the line through the winding of relay 407 during the silent intervals and is superimposed on the alternating current during the ringing intervals. The operating circuitof the ringing interrupter-s is closed bythe operation of relay 400. I i

The attendant may now restore her keys. Relay 407 does not operate on the current which passes through the subscribers bell but as soon as the subscriber answers he closes a path through his telephone set for direct current which operates relay 407. Relay 407 locks up through its right hand winding and connects the subscriber through to relay 420 and opens the operating cirunit of the ringing interrupters. Relay 420 operates, operating relay 401 and as, the station key has been restored to normal, relay 428 also operates. As relay 436 is operated, this causes the operation of relay 437 cutting the line through to the cen tral otlice and operating relays 439 and 440. As relay 422 is operated,'the operation of relay 440 causes the operation of relay 444, the circuit for which may be traced from grounded battery, left hand winding of re lay 444, outer left hand armature and front contact of relay 422, outer right hand armature and front contact of relay 428, front contact and inner left hand armature of relay 440 to ground. Relay 444 locks up to ground on conductor 406 and places the locking circuit of relay 422 under the control of relay 440 and also operates relay 455 under the control of relay 440 which eirtinguishes the guard lamp 448. The operation of relay 440 also bridges the noniuductive shunt 441 across the winding of the supervisory relay 439 and removes the short-circuit from the high resistance winding of the retardation coil 449. The con nection is now in a stable condition and conversation may proceed.

When the subscriber hangs up relays 439 and 440 release releasing 1n turn relays and 455. Relay 432 operates preventing the release of relay 436. fThe bridge through the retardation coil has removed from the line by the release of relays 422 and 455 and the high resistance of relay 432 permits the release of the supervisory relay at the central office. When the disconnection takes place at. the central oflicei relay 432 releases, releasing relay 436. This releases relay 437 and relay 401 which turn release all other operated relays and restores the circuitto normal.

The subscriber may recall the attendant by depressing the switch hoolr momentarily or operating his dial, thus releasing relay 440 momentarily, which releases relay 422. As relay 444re1na1ns operated line lamp.

442 is lighted but relay 455 remains operated preventing the guard lamp 443 from lighting. Relay 455 isslow in releasing so as to prevent'disturbance oi" the apparatus at the central oflice by a momentary interruption of the circuit through the subscribers telephone. The attendant subscriber answers by operating her listening key 440 which bridges her telephone set across the line and causes relay'422 to operate and lock up. In case she has occasion to trans fer the call to another line sheoperates a release key 403 which releases'relays 423, 444, 416, 412, 414, 407, 102 and 122. Relay 455 is released by the release of relay 444 a and guard lamp 448 lights. The attendant -may now operate her station keycomprising the right hand contacts of key 430 and select another station in the manner already described. y

In case the line whichthe attendantselects is busy she may, if the importance of the incoming call appears to justify it, break in upon the conversation by operating key 419. This releases relay 410 and cuts 03' the busy tone and operates the contacts of relays 414 and 407 so that the attendants telephoneset is connected to the called liner iThe release of key 419 does not operate relay 410 again so'thatthe sleeve of the line 412. Relay 412, however, does not operate When the called line becomes free, the reis connected through resistance 411 and relay f moval of the ground from itssleeve permits relay 412 to operateand lock up through relay 416 and operate relay 414. The line .is now connected through to relay1407jso' that the subscribers bell rings and the re mainder ofthe operation. is the same as it the line had not been busy. In case the attendant does not wish to wait for the line to become idle, she may operate the release key 403. after releasing key 419 and then select another line.

In case the attendant subscriber receives an incomingfcall which is notextended to a station she may give the disconnectsignal to the central ofiice by] restoring her listening key andoperating the disconnect key 424. This releases relay 422 opening the bridge through the retardation coil The disconnect key 424 may be used as a flashinglrey for signaling the operator by operatingit when the listening key is operated. This opens the line to the central office releasing the supervisory relay there-- tag at'but relay 439; remains. operated in serieswith the telephone set and resistances 456. and 457, preventingtherelease ofrelay 436.

OaZZs originated by attendant subscriber.

The attendant subscriber may originate a call to the centraloflice operating the listening key. This groundsthe tip of the;

trunk through aback contact ofrelay 436 and a back contact. of relay 404 operating the line relay at the central office. same time the depressionof the listening key 446 operates relay 422 which groundsthe, sleeve of the ltrunk lighting the busyla np 409 and operatingwrelay 400. Vtlhen the operator at. the. central oflice answers relay.

439 operates, operating in turnrelays440.

and 436.

After, the. attendant has originated a. call to the centralofiice, she mayextend it to any stationjustas: if itwere aninconiing call.

The attendant may; call any station. over a trunk by operating. the. station key and.

the listening. key and selecting; the. station in the same mannerasdescribed for-the incommg call. The operation of relay 404 cuts, off the. calling in groundrso'that the linerelay at thecentraloffice is not operated. The. callmay be -extended to the central office by restoring the station key and leaving the listening key operated until the-central office has. answered.

In case of a failure in thebatterysupply. within this system the attendant may call the central oiiice by operating. the. central oflice key comprising" the right hand-cone tacts of key 430, the listening key 446. and the. emergency key 45,8. The central ofiice key in addition tocutt-ing off the bridges across the circuit, places. a noninductiVe shunt across the winding ofrelay 439. Under this condition relay-459 operates as soon as the operator atthe centralofiicean swers, andv removes, the callin gein ground from the line.

Ring mgcircuit;

Whenever any link circuit or trunk circuit is 1n. the ring ng condition relay 340 is operated. Th s'closes a. circult for operating relay 341 which operates. and-locks up and operates relay 34 2, Relay 342 opens:

" the operating circuitofrelay 341 and locks up and short-cirouitsandreleases relay. 341.

Relay 341 in, releasing opens the operating;

circuit of relay. 342 and' short-circuits andreleases it. The releaseof relay 342allows:

relay 341 to operate again and this .cyc leof. operations continues. as long as. relay 340 remainsoperated. Ground isconnected first to oneand then to the other of the-primary. Windingsof the ringing transformer-343 by, the contacts of relay 342 so that-ani alter.- nating current is induced in the secondary At the Winding ofthe transformer 343 as-long as,

the common point of the primaries is connected to. battery through the front contact of relay 344 and the back contact ofrelay 345. Relay 340 also closes an operating circuit for relay 346. which operates and lockstup and operates. inturn relay 347.

Relay 347 inoperating opens the operating circuit of relay 346 and short-circuits and releases it.. Relay 346 in releasing releases relay 34 7, thispermits relay 34.6 to operate again and the cycle of operations is repeated as long asrelay 340 remains operated. Assoont as relay 340 operates, it operates relay 344 through the back contactsof relays 347 and 34'5connecting battery to the pri mary. windings of the ringing transformer 343;- WhenQrelay 347 operates relay 344-is.

locked up through the righthandwinding ofrelay 345 Relay 345 operates removing the. shortcircuit from itsleft hand winding andcuts oti battery from the ringing transformer 343. When relay 347- releases it short=ci rcuits. and releases relay 344 but relay 3451'remains locked up through itsle ft Tone circa-it.

VVheneVer relay 302 of a link circuit or relay 420 of a trunkcircuitisoperated relay 303 operatesand closes a circuit through the back contact and winding of. relay 330. Relay v330 operates. as. a buzzer and supplies busy tone and dial tonev through the link andtrunk circuits.

Buzzer circuit.

Battery is supplied to the line lamps ofthe tr-unks:"through the relay 339 which'operateswhenever a line-lamp is lighted and sounds the buzzer. The key-348 B furnished by means. of which the buzzer may be silenced; even. though the line lamp is burning.. VZhen the relay, 339 is operated and key. 338-isenormal" a circuit is established 3 from: ground, the. armature and. front con-- tact of relay-33 9,, the left hand. Windingof relay 349; the back contact anctarmaturc of relay- 350," the right hand winding of relay 349 togrounded battery. Relay 350 actsas a buzzer and?createsan:audible tone. to attract the attentionofl the attendant subscriber; T

What is claimed is:

said lines, a plurality of saidrelays being employed in establishing a-connection, direc- "tively operable means for energizing a plurality of said relays-normally eifective to energize one of-said' relays, and means responsive to the energization of said one of said relays for controlling said energizing means. i

2. In a telphone system, telephone lines,

groups of relays for establishing connections to said lines, a relay of each groupbeing employed in establishing a connection, directively operable means for selectively energizing said relays, a relay associated with said means, means responsive to the selective energization of a connecting relay of one group for energizing said last relay, and means controlled by said last relay for changing the control of said energizing means from one group of said connecting relays to another group of said connecting relays.

3. Ina telephone system, telephone lines, groups of relays for establishing connections to said lines, a direction switch forpiloting said connections, and a relay associated with said direction switch responsive to the energization of a connecting relay in one of said groups for controlling said direction switch to cause energization of'a connecting relay in another of said groups.

at. In a telephone system, telephone lines, switching devices having permanently paired'primary and secondary contacts for establishing connections to said lines, means for operating said devices to establish connections to busy lines, and means responsive to the removal of the busy condition to automatically render such connections effective.

5. Ina telephone system, a plurality of telephone lines, an operators trunk, a central oliice trunk, switching devices having permanently paired primary and secondary contacts for interconnecting said lines and trunks, means for operating said devices to establish connections to busy lines, and means responsive to the removal of the busy condition to automatically render such connections efl ective.

6. In a telephone system, telephone lines, an operators trunk, switching devices having permanently paired primary and secondary contacts for interconnecting said lines and said trunk, means under control of said operators trunk for establishing a connection to a busy line, and means respona sive to the removal of the busy condition to automatically render such connection efiect-ive. i

7. Ina telephone system, telephone lines, an operators trunk, switching devices having permanently paired primary and secondary contacts for interconnecting said lines and said trunk, n cans under control of said operators trunk for controlling said devices for establishing a connection to a busy line, and means responsive to the removal of the busy condition to automatically render such connection effective. 7

8.In a telephone system, telephone lines, an operators trunk, switching devices having pern'ianently paired primary and secondary contacts for interconnecting said lines and said trunk, a direction switch for controlling said devices, means for operating said direction switch to cause one of said devices to establish a connection to a busy line, and means responsive to the removal of the busy condition for rendering said connection effective.

9. In a telephone system, telephone lines, an operators trunk, a sending dial associated with each of said lines and with said trunk, switching devices having permanently paired primary andsecondary contacts for establishing interconnections between said lines and said trunk, a direction switch separate from said interconnections for controlling said devices, said direction switch being responsive to the manipulation of said dials, and means responsive to one operation of a said switching device for controlling sain direction switch.

10. in a telephone system, telephone lines, an operators trunk, a sending dial individally associated, with each of said lines and with said trunk, groups of switching devices having permanently paired primary and secondary contacts for establishing interconni-ictions between said lines and said trunk, a switching deviceo't each group being required to complete a connection, a direc ion switch separate from said interconnections ior controlling said devices, said direction switch being responsive to the manipulation of said dials, and means individual to said direction switch responsive to the actuation of a switching device of one of said groups under the control of said I direction switch for transferring the control off said direction switch to another otsaid groups of switching devices.

11. In a telephone system, telephone lines, relays for establishing connections between said lines, a plurality of said relays being employed in establishing a connection, direction switch separate from said established connection for controlling the operation of said relays, said direction switch being normally effective to cause the energization of one of said relays, and a relay associated with said direction switch responsive to the energization of said one of said relays for transferring the control of said switch to another of said relays.

12. Ina telephone system, telephone lines, relays for establishing connections between said lines,.said relays being, divided into groups and a relay of each group being employed in establishing a connection, a direction switch separate from said established connection for controlling the operation of said relays, said direction switch being normally effective to cause the energization of the relays of one of said groups,

and a relay associated with said direction switch responsive to the energization of one of said relays of said one of said groups for transferring the control of said switch to another of said groups.

13. In a telephone system, a telephone line, a central 'oflice trunk, a relay under control of said line for placing a calling condition'on said trunk, a source of current for energizing said relay, other means under control of said line for placing a calling condition on said trunk upon failure of said source of current, and a normally inoperative relay controlled in part by said means, said last relay being responsive to the extension of saidrcentral otlice trunk to remove said calling condition.

14. In a telephone system, a telephone line, aoentral oitice trunk, means at one end of said trunk for connecting said line'thereto, means at the other end of said trunk for indicating av calling condition thereon and for extending said trunk, means associated with said line for placing a calling condition on said trunk, a relay for removing said calling condition responsive to the extension of said trunk, a souree of current for energizing said relay, a normally inoperative relay independent of said source of current for removing said calling condition, and meansior-rendering said last relay operative upon failure of said source 0t 1 current.

15. In a telephonesystem, telephone lines, link circuits, switching devices having, permanently paired primary and secondary contacts for connecting said lines to said links, a mechanism normally eiiect-ive to ren der said links selectable in the order of their sequence, a starting circuit for governingthe control of said switching devices, said starting circuit including a relay arrangement common to said link circuits arranged to measure time. against the operation of said switching devices to chai'ige the order of selectabil-ity of said links and to transfer said starting circuit to another switching device-upon:the -failure of one of said devices't'o connect a line to walinkwithin a predetermined time 16. In: a t'elephonesystem, telephone lines, link circuits, switching devices having permanently paired? primary and" secondary contacts fonconnectingisaid lines to said links, a mechanism normally eflective to render said links selectable in the order of their sequence; a. starting circuit for controlling said switching devices, said starting circuit including a relay arrangement comprising a plurality: of slow relays common to-said link, circuits" arranged to measure time against the-operation of said switching devices to change the order of selectability of said' links:and to transfer said starting circuit to another switching device upon the failure of one of said devices to connect aline to alink within predetermned time; i r

17. 111 a telephone system, telephonelines, lllllLCll'CLlltS, switching devices having permanently paired primary and secondary contacts for connectingsaidlinesto said links, a starting circuit arranged to normally cause the operation of afirst-in-order switching device, said starting circuit having associated with. it. a relay arrangement for measuringtime,v said relay arrangement being arranged to transfersaid' starting circuit to a second-in-order switching device upon the failure of said first-in-order switching device; to operate Within a" predeterminedtime, to thereafter transfer said starting circuit to: a third in-order switching device upon the failure of said second in-order switching device to operate within a predeterminedtime, and to" thereafter transfer said starting circuit in the. manner aforesaid any desired number of times.

In witness where-0L1 hereunto subscribe my name this 8th. day of January A. 1);,

EDlVAB-D E. HINRIGHSEN;

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