Patent GB-226154-A (GB)
Title: Improvements in or relating to telephone systems
IPC: H04M19/00
Filed: 1924-06-18
Abstract: 226,154. Automatic Telephone Manufacturing Co., Ltd., (Assignees of Wicks, J.). Dec. 14, 1923, [Convention date]. Automatic and semi-automatic exchange systems and apparatus; metering.-Relates to means for meeting the supervisory requirements of 'both automatic and manual exchanges when calls are made between manual and automatic subscribers during the transition of a large network from manual to automatic working. A multi-office system is described comprising not more than ten districts each comprising not more than ten offices, some of which may be manual and others automatic. Inter-office calls are made over a district selector repeater, such as D, Fig. 1, and an office selector repeater, such as E, Fig. 2. In making a call, when the wanted line is found, dialling loop battery and earth are disconnected at the office selector repeater from the trunk leading to it, and are substituted by a front bridge high resistance relay, this change bringing about the switching through of the connection at the district and office selector repeaters. When the wanted party replies a portion of this high resistance relay is short-circuited, and a marginal relay in the district selector repeater responds, causing the meter to be actuated if the calling subscriber belongs to an automatic exchange, or initiating the operation of an answer signal if the call is made through a manual operator's position. Automatic subscribers or manual operators may also set up calls automatically to a trunk operator, or to a " zero " operator who can extend calls manually or automatically and who is reached by dialling the digit O. In either case the automatic connection may be held and the engaged trunks marked busy, by the response of a differential relay in the district or office selector repeater, which relay pulls up responsive to battery being connected to one line conductor at the trunk or zero operator's position. Other features of the system described are claimed in the divided Specification 238,245. Connection from automatic subscriber A, Fig. 1, to automatic subscriber A<1>, Fig. 4, at distant exchange; district selector repeater D, Fig. 1. A calling subscriber A is extended to an idle district selector repeater D by a line switch C, in known manner. The line relay 31 energizes the slow release relay 32, which prepares the circuit of the vertical magnet 43, and completes a circuit 46, 51, 64 for the upper winding of a relay 37, which energizes a relay 38. Dialling tone is now sent to the calling party over armatures 68<1>, 55, and on the transmission of the first digit the vertical magnet 43 steps up the wipers in the usual manner. The response of the parallel relay 33 closes a circuit 53, 62, 56, 76, 45 for stepping relay 34, which locks up over the interrupter contact 42 of the rotary magnet 41. On the cessation of the vertical impulses, the relay 33 relapses and closes a circuit for the rotary magnet 41, which opens the locking circuit of the relay 34 and rotates the wipers 79 - - 81 on to the first contact set in the selected level. The rotary magnet 41 and the stepping relay 34 operate alternately in well-known manner, until an idle trunk 85, 86 is engaged, on which the switching relay 39 energizes, disconnects dialling tone, and connects a bridge including the upper winding of the relay 37 across the seized trunk 85, 86. The line relay 101, Fig. 2, of the seized office selector repeater E energizes in series with the relay 37, which maintains the relay 38 energized, thereby preventing the response of the switch-through relav 35. Office selector repeater E, Fig. 2. This operates in response to the second digit in substantially the same manner as the selector-repeater D, Fig. 1, to select an idle trunk, such as 161 - - 163, leading to an idle thousands selector F, Fig. 3, in the wanted office. The line relay 101 closes a circuit for the lower winding of a relay 105 which energizes a relay 108 : these relays correspond to similar relays 37 and 38 in the selector D. During impulsing, the relay 38 is maintained energized by the parallel relay 33 over armature 56. When the idle trunk 161 - - 163, Fig. 2, is engaged, the switching relay 111 responds, energizes relay 109, and connects a bridge including the line relay armature 126 and the lower winding of the relay 105 across the outgoing trunk 161, 163, thereby causing the response of the line relay 201 of the selector F, Fig. 3. Thousands and hundreds selectors, F. G, Fig. 3. These selectors are provided with combined release and change-over relays 202, 252. On the response of the line relay 201, the relay 202 energizes over the vertical off-normal spring 211, prepares a circuit for the vertical magnet 207, and connects the line relay armature 221 to the. release conductor 162 over armature 213 to enable the selector to release if the calling party hangs up without dialling another digit. When the subscriber dials the thousands digit, the impulses are repeated by the armatures 51, 126 at the selector repeaters D, E, and upon each relapse of the line relay 201, the vertical magnet 207 is energized over the grounded release conductor in a circuit 213, 228, 221, 223. At the first vertical step, the stepping relay 203 is energized over the vertical off-normal springs 210, and locks up over the interrupter contact 209 of the rotary magnet 208, the circuit of which is prepared at armature 224. During impulsing, the relay 202 is energized in parallel with the vertical magnet 207, but at the end of the impulses this relay relapses, prepares the release circuit at armature 223, and at armature 224 clcses a circuit, which also includes the release conductor 162 for the rotary magnet 208. The stepping relay 203 and the rotary magnet 208 now interact in the usual manner until an idle hundreds selector G is engaged, when the switching relay 204 pulls up, switches through, disconnects the line relay 201, and at armature 228 opens a point in the circuit of the release magnet 205. The seized selector G is actuated in the same manner by the hundreds digit and selects an idle connector H, Fig. 4. Connector H, Fig. 4. The ring cut-off relay 303 of this switch also functions as the changeover relay. The line relay 301 energizes across the engaged trunk over vertical off-normal springs 307, 308 and closes a circuit 339, 331, 321, for the release relay 302, which locks up over armature 324 and the release conductor 242, shunts the off-normal springs 307, 308, and prepares the impulsing circuit at armature 325. The combined change-over and ring cut-off relay 303 energizes in parallel with the relay 302 and extends the impulse circuit to the vertical magnet 313, which steps up the wipers on the receipt of the tens digit. The impulse circuit extends from the grounded release conductor 242 over the circuit 339, 331, 321. 325. Upon the first vertical step the springs 307, 308 open leaving the line relay under the control of the relay 302. Relay 305 energizes in parallel with the vertical magnet 313, and holds relay 303 energized over armatures 334, 350 after the off-normal contacts 309 are opened. At the end of the tens impulses, the relays 305, 303 relapse and the relay 303 transfers the impulse circuit to the rotary magnet 312, which on the receipt of the units digit rotates the wipers to the wanted line. During these impulses the relay 305 is maintained energized to connect the test wiper 342 to the busy relay 304, and to shunt the armature 331 and so prevent release if the test wiper passes over a busy test contact. Busy test, signal, and release. If the wanted line is engaged the busy relay 304 is energized, locks to the release conductor 242 on the relapse of relav 305, and connects up the busy tone lead 175. Relay 305 de-energizes release relay 302, which opens the circuit of the line relay 301 and causes the switch-through of the connection as described in the next paragraph. The calling party on hearing the busy tone, hangs up and releases the connection as described later. Completion of connection, talking current, metering. If the wanted line is idle, on the relapse of relay 305, the switching relay 306 energizes over its upper winding in series with the switching relay 347 and stepping magnet 349 of the called line switch C<1>, locks up over armature 338, and connects up the line wipers 341, 343, whereby ringing current passes over the upper winding of the combined change-over and ring cut-off relay 303 to the called line. The relay 306 also de-energizes relay 302, which disconnects the line relay 301. and causes the relapse of relay 105 in the selector repeater E, Fig. 2. Thereby the relays 108, 109 are de-energized, and a circuit is completed for the switch-through relay 110, which locks up, removes ground from the lower trunk 86, disconnects the line relav 101 from the upper trunk 85, and completes a local circuit 140, 142 for it, and bridges a high resistance relay 107 across the condenser between the left-hand windings of the repeating coil. The slow-release relay 109 is held up whilst the preceding selector D is switching through as described later, a temporary bridge extending through the upper windings of the relays 106, 105, and through the lower winding of the relay 106, being connected across the wipers 153, 155. In response to the disconnections of battery and earth from the trunks 85, 86, the relay 37, Fig. 1, de-energizes and disconnects relay 38, which closes a circuit for the switchthrough relay 35. The relay 35 locks up, and bridges the lower winding of the relay 37 and the upper winding of the relay 36, and the lower winding of relay 36, in series across the wipers 79, 81. Neither of these relays responds, the relay 36 because it is differentially wound, and the relay 37 due to the high-resistance of relay 107, Fig. 2, which now responds and closes a circuit for relay 101 independent of relay 109, which shortly a