Patent GB-258934-A (GB)
Title: Improvements in automatic and semi-automatic telephone systems
IPC: H04Q3/00
Filed: 1925-06-29
Abstract: 258,934. Standard Telephones & Cables, Ltd., Lowry, L. P., and White, C. G. June 29, 1925. Automatic exchange systems.-A vice for testing impulse transmitters indicates the number of impulses received from an instrument on test during a measured time interval. The device may be located at a test desk at the exchange and in the arrangement described comprises a bank of lamps associated with a stepping switch SW, to the magnet R of which the impulses are repeated for a predetermined period, say 1 second, measured by a timing device such as a pendulum. When the device is connected to a subscriber's dial by throw. ing the key CK a. line relay A energizes over the subscribers' loop and energizes a slow-release relay B which locks up over its upper armature. A circuit is thereby closed for the lower winding of a two-step relay K which closes its fly contacts 5, 6. On the subscriber dialling, a stepping circuit A 6, 5, B 9, 10, C 12, 13 is completed for magnet R each relapse of the relay A advancing the switch SW a step. On the first relapse of relay A a circuit is also closed for a relay E which energizes a magnet PM which starts the timing pendulum PM 6. Directly the pendulum leaves contact PM a a short-circuit is removed from the upper winding of relay K which operates fully, opening the circuit of magnet PM. The pendulum is timed to swing back in one second, and at the end of this period relay C energizes, disconnects the stepping magnet R from control by relay A and closes an alternative circuit for it over contacts 13, 11 to ensure its complete energization in case relay C energizes at the moment of a relapse of relay A. A pair of lamps is allotted to each position of the switch SW subsequent to position 3, one of each pair being connected to contacts wiped by brush 3 and the others to contacts wiped by brush 1; which lamp of a pair is lighted indicates whether the relay A is energized or de-energized when relay C responds on the expiration of the time period. If at this instant relay A is energized, a circuit is closed for relav P, which locks up and disconnects relay D, and the lower lamp of a pair depending on the position of switch SW is energized over brush 3. Should, however, relay A be de-energized, relay D responds, locks up. disconnects relay P, and closes the circuit of the upper lamp of the selected pair over brush 1. The device is released by throwing the reset key RK and unlocking relay B which de-energizes relays K, C and closes a circuit for the release magnet Z of the switch SW over brush 2. The relay P or D is held energized over a brush 2 and prevents relay B from again energizing until the switch SW has restored. If before dialling, the subscriber momentarily depresses his switchhook, the effect is the same as when a single impulse is dialled. Should the relay A remain de-energized long enough for relay B to relapse the switch SW is released as before and the device is restored to its prepared condition. In the event of relay B not relapsing and the subscriber dialling before the termination of the time period, the switch SW will not be stepped during the remaining part of the period past the first three contacts and when relay C responds a '' false impulse " lamp FI at the top of the bank will glow. The lamp FI will also glow if the subscribes dials less than the stipulated number of impulses. The attendant releases the device as before.