Patent GB-272628-A (GB)
Title: Improvements in or relating to telephone systems
IPC: H04Q3/42
Filed: 1926-03-22
Abstract: 272,628. Automatic Telephone Manufacturing Co., Ltd., and Ostline, J. E. March 22, 1926. Semi-automatic exchange systems.-In a telephone system in which numbers transmitted from an automatic to a manual exchange are shown on a call indicator at an operator's position, a register set is associated with the trunk in use by means of a hunting switch which is arranged to switch the call to a special or ordinary operator's position if the calling subscriber dials prematurely. The hunting switch RS has separate test wipers for hunting for an idle register set or an idle operator, the seven register sets being multipled three times, for instance, in a 25-point switch, with four operator contacts, the operator contacts in the row swept over by the register test wiper being permanently earthed and viceversa. Certain positions may be made dead and arranged so that the all-registers-busy relay will connect busy tone thereto to provide for the possibility of a switch RS hunting when all registers become busy. The impulses are sent to the register set over a forward loop having the source of energy at the automatic exchange. The call indicator operator may use any cord to connect up to the wanted line, a finder switch associated with the cord being set into action by the plugin operation to find the calling; line. The trunk is busied if the calling party hangs up before the operator answers and all trunks are busied when the operator removes her head set. If an incomplete number is dialled it is displayed, and the operator then presses the busv key. Duplicate lamp panels and display control switches are provided. Rotary line switches may be provided at the incoming end of the trunks under the control of a load distributing switch, as in Specification 229,371. Secondary preselecting line switches may he used to find the repeater as in Specification 169,698. Specification 214,195 is also referred to. A relay 58 primarily operated over a low-resistance upper winding removes a short circuit from its lower winding and remains energized over the whole winding. Seizure of idle register. When the outgoing repeater at the automatic exchange is taken into use, relays 5, 12 energize, so that the polarizing winding of relay 24 is energized and a circuit is completed for relay 62 in the incoming trunk relay group at the manual exchange [battery, upper winding of 62, armatures 72, 82, 95, lead 50, armatures 7, 4, lower winding of relay 24, armature 34, upper winding of relay 28, armature 8. lead 51, armatures 98, 84, 73, lower winding of relay 62, armatures 65, 86, lead 156, earth]. Relay 64 operates, directly earths relay 62, and energizes relay 200, (earth, relay 200, armatures 208, 67, 83, low resistance upper winding of twostep relay 58, battery). The switch RS now steps in a circuit [earth, test wiper 211, armatures 206, 201, magnet 203, battery], to find an idle register when the short-circuit is removed from relay 204, which busies the register at armature 206, locks itself at armatures 207, 208, and cuts the circuit of relay 200 which releases slowly so that relay 58 energizes and locks up over both windings and armatures 60, 68. Relay 221 energizes over wiper 213, thus energizing relay 225. Registration of digits. When relay 5 is deenergized by the first impulse of the wanted subscriber's number, 3456 for instance, relay 13 energizes short-circuiting the lower winding of relay 24, and relay 62 de-energize so that relay 71 operates. When relay 5 pulls up again, relay 78 energizes (earth, armature 15, lead 51, armatures 98, 84, 73, relay 78, armatures 72, 82, 95, lead 50, armatures 7, 14, battery), and sends an impulse, in a circuit (earth, armatures 80, 61, 93, 57, lead 153, armature 205, wiper 212, relay 227, wiper 254, magnet 255, battery), to advance wiper 256 of the first digit register switch M1 one step. Relay 74 also energizes, and in turn completes a further circuit for relay 71, and energizes relays 69, 62. Relay 227 operates and energizes relay 239. Two more impulses are now sent through relays 5, 78 to the magnet 255. Relays 13, 78, 74, 62, 69, 71 then de-energize in turn when relay 62 pulls up again in its original circuit. Relay 69 being slow to release, the circuit of relay 71 is kept open while relay 62 is deenergized. Relays 227, 239 de-energize, and in doing so energize magnet 250 to advance the switch M one step. Four, five, and six impulses are sent in turn to the switches M2, M3, M4, and when the switch M is finally stepped to its fifth contacts, relay 229 is energized over the wiper 253, pilot lamps 257, 258 are lighted and relays 300, 303 energized. A circuit is formed for magnet 306 and relay 307 in series, and the wiper 310 of the distributing switch DS1 is stepped round, the relay 307 being short-circuited since the contacts of the switch DS1 are normally earthed (see armature 232). When wiper 310 reaches a contact 311 which is not earthed, relays 307, 235 energize in turn, releasing relay 303. Relay 242 energizes over armature 238, and relay 85 energizes over lead 151 and armature 237, opening the impulsing circuit at armature 93. Relay 85 locks up over its lower winding. and armatures 89, 97, 83, 60, 68. Circuits are now formed from earth at armatures 238 over the wipers of the switches M1 - - M4. contacts of relays 270. required lamps in panel L, relay 287, battery. The lamps indicate the required number and relay 287 operates a meter 290. Wanted subscriber busy; release of connection and register. The operator tests the jack of the wanted subscriber with the plug P, Fig. 1, and battery on the bush closes a circuit over lead 160 to the primary of an induction coil. which produces a click in the receiver 291. The operator then presses busy key 276, which earths the leads 158, 157, to hold the register, and earth lead 159 to energize relay 81 which disconnects relay 62 and connects itself across the leads 50, 51 so that busy cone is transmitted from lead 99. The operator restores key 27, relays 64, 85, 58 deenergize, and when the calling party hangs up, relays 5, 12, 81 will release in turn and the preceding selectors will return to normal. When earth is removed from lead 157 by key 276, relay 204 releases, so that relays 221, 225 release in turn, rendering the register again selectable. homing circuits are formed for the switches M - - M4 irom armature 223, pilot relay 247 and off-normal contacts 252, and when the wiper 253 steps on, relays 229, 235 release, and release relay 300 it no other call is waiting; relay 307 also releases, and the set is ready to complete another call. Wanted subscriber idle. On plugging in, sleeve relay 136 energizes in series with lamp 140, which does not light, and relay 101 pulls up over armature 138. Magnet 108 is connected to wiper 109, and the finder switch F steps around until the contact 100 from which earth has been removed is reached. Relay 105, previously shortcircuited, is now energized. Relay 94 then operates and locks up. Relay 62 de-energizes, releasing relays 64, 85 in turn, and removing earth from lead 157 so that the register set releases as before. When relay 105 operated, relay 101 released, and the speaking leads were connected through, so that relays 120, 115 operate. Relay 105 is now locked over armatures 107, 118, and relay 112 operates and locks up. Relay 127 now operates (ground, called party's cut-off relay, jack bush, plug sleeve, relay 136, armatures 104, 116, 139, 133, 135, relay 127, battery), and connects ringing current from lead 132 to the wanted line. The small condenser 130 allows ringing tone to leak back to the caller. When the called party replies, the trip relav 131 operates to remove the short-circuit from relay 134 which connects up battery at 135. thus shorting relay 127 to stop ringing and complete the talking circuit. Relay 125 operates the reversing relay 122 so that the polarized relay 24 is energized. and operates reversing relay 30, which earths the metering lead 4, and inserts the whole impedance 28 in the line circuit to improve transmission. Release of connection. When the called party hangs up, relays 125, 122, 24 and 30 release. When the calling party hangs up, relays 120, 115, 105, 94 release in turn, restoring the trunk relay group to normal. Relay 134 is also cut out by the release of relay 115. and removes the short-circuit around the lamp 140 due to the low resistance of relay 134: lamp 140 lights. whereupon the operator removes the plug, and relays 136, 112 and lamp 140 de-energize. Supervisory lamp signals. In addition to the disconnection signal above, the lamp 140 also gives warning of failure of switch F to find, or premature removal of plug. While switch F hunts, relav 101 connects interrupter 110 to the function of lamp 140 and relay 136, so that the lamp is flashed, Similarly, if the plug is, prematurely withdrawn, release of relay 112 connects up interrupter 111 over armatures 113. 117. 104. Number dialling before a register set is seized. While switch RS is hunting, relay 58 is partially energized. If the impulsing now begins, relay 78 energizes and partially operates relay 52 over its armature 80, so that armature 54 pulls up. Relay 78 de-energizes immediately and relay 52 fully operates connecting leads 50, 51 to 151, 153 respectively, and at armature 56 changing from test wiper 211 to 210. The switch RS now continues to hunt until a contact such as 321 connected to a free operator's jack J is reached. Relay 204 now operates, and connects earth to wiper 213 so that relay 326 operates and lights a lamp 332. When the operator plugs in, sleeve relay 328 extinguishes lamp 332 and connects impedance 333 across the speaking leads. The operator can now throw the listening key and make the connection or explain the situation. Release of connection to operator. When the calling party hangs up, relay 5 releases and the repeater r