Patent GB-266794-A (GB)
Title: Improvements in telephone systems
IPC: H04Q3/00
Filed: 1925-11-24
Abstract: 266,794. Standard Telephones & Cables, Ltd., Baker, J. H. E., Moscrip, W. R.., and Chanter, A. J. Nov. 24, 1925. Automatic and semi-automatic exchange sustems.-When a first code selector is freed at the calling end, release is delayed for an interval determined by the successive relapse of three sluggish relays P, BF, B, in order to give time for the succeeding switches to restore. Further, in the case of a call to an operator's position or of a busy condition at a succeeding switch, release is positively prevented by the energization of the line relay L over the lower line wiper until the operator clears or until busy flash battery is cut off. The outgoing trunk is guarded at a front contact of the switching relay H. A first code selector which is taken into use by an operator is described, with means for testing the switch and for dealing with various irregularities. Normal connection. When the operator plugs in, sleeve relay Q energizes, lighting the position lamp and grounding the test wire RT, and line relay L and release relay B are connected up. Impulse relay A and change-over relay C (upper) also operate over contacts of relays L, B. The magnet DM and switching relay K are now connected to the test wiper PW to hunt for an idle A ' digit switch in the usual manner. Relay K energizes and locks when this is found, connecting line relay L over wiper PU to battery through the impulse relay of the A' digit switch, impulse relay A across wipers + W, - W and busy relay BF to wiper AB. Dialled impulses are received by the ' A ' digit switch and register-controller, and the impulses sent out therefrom are repeated by relay A at contact 5 to the vertical magnet V, sluggish relays P (upper), C (lower) being in parallel therewith. Relay P energizes and locks, while relay C falls back at the end of the first train of impulses, its original circuit being opened at off-normal springs N2. The rotary magnet R is then connected up, and relay A serves as a stepping relay, being connected to the test wiper P over contacts 10, 11, 8. When an idle trunk is found, switching relay H, being no longer short-circuited, energizes in series with relay A over contacts 6, S4, 16, locks, grounds test wiper P and connects wipers + L, - L to wipers + W, - W, so that further impulses are sent directly over the trunk. When the register-controller and ' A ' digit switch release, ground is removed from wiper PW, and relay K falls back, connecting up sluggish relay BF and disconnecting relays L, B. Release. When the operator removes her plug, relay Q falls back and removes ground from test wire RT. Relay P relapses, disconnects relay BF and re-energizes line relay L over contacts 31, 15. Release relay B re-energizes, grounding test wire RT, so that relay R operates and marks the switch busy pending release. When relay BF relapses, in the ordinary case relays L, B, H fall back in turn, and the release magnet Z operates to restore the switch to normal. Line relay L, however, upon the relapse of relay BF is connected over contact 9 to wiper + L, and if this wiper is connected to battery in the case of a call to an operator's position, or in the case of a busy condition being reached at a succeeding switch (battery period of busy flash), this relay prevents release of the switch until this battery is removed All trunks busy. Contact springs S are operated in the 11th rotary position. Relays A. H are disconnected, and test wiper P is grounded. Further impulses have no effect therefore, and when ground is removed from wiper PW, relay K falls back and energizes busy relay BF, which connects busy flash to line relay L. When the operator clears, relays Q, P, BF fall back and the release magnet Z is connected up. ' A ' digit switch finds no idle outlet. In the 11th rotary position, ground is connected to wiper AB, causing busy relay BF to energize and connect busy flash to line relay L. This relay is short-circuited at the battery period and falls back, releasing relays B. C. and relay P now energizes and locks, also locking relay BF. Relay K falls back when ground is removed from wiper PW, and disconnects relay A. Busy flash continues until the operator clears. Premature dialling. Relay K has not energized when this occurs. Line relay L repeats the first impulse at contact 7 to impulse relay A so that the vertical magnet V raises the switch one step, relays P (upper), C (lower) being operated in parallel. The original circuit of relay C (upper) is now opened, and relay BF energizes over springs N9, opening the holding circuit of relay C, so that this relay falls back and disconnects the vertical magnet V. Meanwhile, relay P energizes and'disconnects relay A, opening the energizing circuit of relay K at contact 12. Further impulses therefore have no effect, and the switch remains in this condition until the operator clears. Omission to dial. A timing device operates in the 'A' digit switch and connects ground to wiper PU, short-circuiting line relay L, which falls back, following by release relay B. Relay P (lower) energizes, and relay C (upper) relapses, and impulse relay A now holds locally over contacts 10, 11, 6. When ground is removed from wiper PW, relav K falls back, releasing relay A, but re-energizing relays L, B. Dialling at this time has no effect, and the switch remains until the operator clears. Faulty or insufficient dialling. Ground is connected as in the previous case to wiper PU, releasing relays L, B. In this case, however, switching relay H is operative, and impulse relay A has already been disconnected. Relay M therefore energizes, locks, opens the loop circuit of line relay L and connects up relay BF. Moreover at contact 17, relay P is disconnected in the same way as upon release, and relays BF, L, B function as already described to restore the switch to normal. When relav K is released over wiper PW, relays L, B re-energize and the switch takes a vertical step as in the case of premature dialling, and remains until the operator clears. Testing. To test the switch as an isolated unit, jack springs T1, T5 are bridged, and springs T3 are bridged through a dial. Relays L, B, M energize, and the last relay prevents magnet DM and relay K from operating. Relays A. C energize and dialled impulses are repeated by relay L to relay A and thence to the vertical magnet V. Relay P energizes at the first step, and change-over relay C falls back at the end of the train and brings in the rotary magnet R. Relay H cannot energize however since relay K is not operated. To test the switch in conjunction with the register-controller apparatus. jack springs T5 are not connected. so that relav M does not energize. and the operations take place as in an ordinary call. Specification 254,003 is referred to.