Patent GB-380458-A (GB)
Title: Improvements in or relating to telephone systems
IPC: H04Q3/58
Filed: 1931-05-14
Abstract: 380,458. Automatic exchange systems. AUTOMATIC ELECTRIC CO., Ltd., Strowger Works, Liverpool, DEYES, H. S., Springfield, Bridle Path, Eastham, Wirral, Cheshire, CORNER, A. C., 26, Pinfold Road, Streatham, London, and BEALE, C. E., 59, Towers Road, Wavertree, Liverpool. May 14, 1931, No. 14348. [Class 40 (iv).] A bi-directional connector responds to a preliminary digit which determines the direction in which ringing current is to be applied to a two-party line and then drops back. The invention is described with reference to three connecting circuits. The 1st, Figs. 1 and 2 (not shown), is for a small satellite office and comprises, in addition to the connector, a singlemotion switch which hunts for a junction to the main office as soon as the circuit is seized. The connector, which has an additional vertical wiper, responds to the 1st 3 digits, dropping back after each unless it is determined that the call is for the main office and the value of the last of these determines in which direction ringing current is to be applied to the line. The 2nd system, Figs. 3 and 4, is generally similar, but the connector has two sets of wipers and the last discriminating digit also effects wiper selection. The 3rd system, Figs. 5 and 6, is for a small office not a satellite. In this case there is no single-motion switch and the connector itself if set in response to one or more of the 1st 3 digits to a position indicating an outgoing connection, hunts for a junction. The systems can be modified for 4 or 3-digit working. Double wiper connector for use at satellite, Figs. 3 and 4. When the finder (not shown) switches through, line and release relays 1A, 1B pull up and 1JFS hunts for a junction to the main office under control of 1K. When the main office is ready or if all junctions are busy, dialling tone is sent back. The first digit is repeated over the junction and to the vertical magnet 1VM in paralell with dialling relay 1C. If it indicates an outgoing call (1 to 5 or 7 to 9) 1JS operates on the relapse of 1C, prevents further action on the local circuits, and if necessary sends back busy tone from the last terminals of 1JFS. If the call may be local (1st digit 6) 1HA is energized and energizes release magnet 1ZM. When the off-normal springs are restored, 1DA pulls up, releasing 1HA and changing the discriminating circuits so that if the 2nd digit has any value but 5 1JS operates as before but if it is 5, 1HB operates and releases the discriminator. When the springs change over, 1DB operates, releases 1 HB, and changes the discriminating circuits so that if the 3rd digit is 1, 2, 3, 8 or 9, 1JS pulls up but if it is 4 or 5, 1HA and if 6 or 7, 1HB pulls up and energizes the release magnet. 1HA or 1HB locks in series with 1HC which releases 1K to release the main office. The fourth digit raises the switch as before but the relapse of 1C in this case energizes 1E to transfer the impulsing circuit to the rotary magnet RM. Ringing. If the line is idle, H pulls up in series with the cut-off relay and applies ringing current to one or other line wire according as PL, which is controlled by the vertical wiper after the 3rd digit, is or is not energized, i.e. according as the hundreds digit was odd or even. Pending the relapse of 1E, the ringing current is continuous from CNR. When the called party replies, IF completes the talking circuit. Connector for non-satellite office. Figs. 5 and 6. When the switch is seized, 2A and 2B pull up followed by the ring cut-off relay 2F. The first 3 digits are repeated to the vertical magnet unless it is determined by the energization of 2JS that the call is an external one. In this case the local back bridge relay 2D is replaced by the bridge 2DJ, 2RI, 2E pulls up and the rotary magnet interacts with 2G, until an idle line is found 2C being energized in parallel with the magnet. 2G is then held temporarily over the test wiper, 2C, 2E fall in succession, 2H switches through in the interval between the relapse of 2C, 2E, and ultimately 2G falls back. If all junctions are busy, 2G is held energized over 11th step springs and the relapse of 2E connects up busy tone. If the 1st is a local digit, 2HA restores the switch and 2DA pulls up when the switch is restored, releasing 2HA. If the 2nd also is a local digit 2HB and 2DB operate in a similar way. The 3rd local digit energizes 2HA or 2HB and on the restoration of the switch 2HC pulls up and releases 2F. The switch then responds to the two final digits in the manner of a final selector, 2E operating at the end of the vertical digit to change over the magnets. At the end of the last digit, 2C, 2E fall in succession and if the line is idle 2H pulls up in the interval. If the line is busy, the relapse of 2E energizes 2G and busy tone is sent back. Ringing. 2H connects ringing current to one of the line wires according to the condition of 2HA, 2HB as determined by the hundreds digit, continuous ringing current being connected first for a short period timed by 2E. Zero calls. If O is dialled, 1MO or 2MO is operated, energizes 1JS or 2JS and disables the forced release and metering circuits. 3 and 4 digit working. The circuits are modified so that the HC relay operates after the 1st or 2nd digit. Forced release. Some time after the seizure of the switch, timing equipment of the kind described in Specification 375,380 energizes 1FD or 2FD to transfer the circuit of the release relay 1B or 2B to the wire ZHL which after a further interval is disconnected. Unless 1FD &c. has previously been released by the zero calls relay or the back bridge relay, the release relay falls back to free the circuit and the calling line remains isolated from the exchange circuits until the subscriber hangs up or the fault is cleared. Metering. On the operation of the local back-bridge relay 1D, booster battery is connected to the private wire during the release tune of J unless J has previously been released by 1MO. In outgoing calls, 1D is energized in a local circuit by the supervisory relay 1DJ. In the other systems, metering is done over a 4th wire, relay J being omitted.