Patent GB-403220-A (GB)
Title: Improvements relating to telephone systems employing automatic selectors
IPC: H04M15/10
Filed: 1932-12-06
Abstract: 403,220. Automatic exchange systems. SIEMENS BROS. & CO., Ltd., Caxton House, Tothill Street, Westminster, DIXON, R. G., 162, Westmount Road, Eltham Park, London, and LONG, D. P., 3, Ingleby Way, Chislehurst, Kent. Dec. 6, 1932, No. 34556. [Class 40 (iv).] Zone metering is controlled by relay sets connected to the outgoing ends of, and individual to, inter-exchange junctions, in accordance with a train of impulses sent from a register-translator in addition to the routing digits. The relay sets include a transmission bridge, and after the first (metering) train of impulses has been received and recorded on a switch, a through metallic circuit is switched in, so that subsequent trains have no effect on the relay set, the bridge being replaced in response to a signal from the register-translator when all the digits have been sent. The switch may select a metering circuit but, as described, is adapted to send metering impulses. When the relay set is seized, relay A operates in series with ballast resistances BR (functioning as described in Specification 372,004), and B operates I (i) over bank DS3 of a switch which records the metering train and subsequently controls metering. Relay I grounds the incoming third wire and completes a circuit for DM which takes a single step over DS1 to operate C (ii) which prepares the impulse circuit for DM over C (i) and operates BD. The metering train (an odd number of impulses) from the register-translator is repeated by A to DM and H pulls up over DS4, whatever the value of the train, when C holding over C (ii) during the train, relapses. Relay H completes the through metallic circuit and A relapses without effect since B is held by BD. When the switch setting trains have been transmitted, booster battery temporarily applied from the register-translator to the third wire operates E (i) over a rectifier RE which prevents current flow from other relays connected to the third wire. E locks up over E (ii), releases I (i), connects holding ground from a contact of the metering relay to the third wire, completes the outgoing loop over I (ii), D, and releases H which replaces the feed bridge. When the called party replies, battery reversal operates D which releases BD (i) to operate a common start relay SR of interrupter equipment FE. This equipment may be already in operation in another call and if the circuit of BD (i) is opened when fe is closed, BD holds over (ii) until the end of the impulse to prevent a clipped impulse. The impulses from FE step DM over DS5 until the switch reaches position 12, metering relay M being operated over DS4 on alternate steps to connect booster battery impulses to the third wire Metering trains of 1, 3, 5 &c. impulses from the register-translator thus give rise to 5, 4, 3, etc. booster impulses respectively. It will be seen that during metering, SR is held independently of the condition of relay D while release relay B is held alternately by M and over DS4 independently of A, so that metering cannot be interfered with by the calling or called party. If the calling party clears first, A and B relapse followed by E and DM steps over DS1 to last contacts whereupon it takes a single step over DS3 to normal. If the called party clears first, the relapse of D lights an alarm lamp AL until it is extinguished by the relapse of E when the calling party clears. According to the Provisional Specification, dualling relay C operated when the relay set is seized, opens the outgoing junction wires and, when it falls back at the end of the metering train, switches in the through metallic circuit. Cam controlled metering is also described. Wanted line busy. Tone warns the calling party who, on clearing, releases A, B, BD and E. The flash intermittently releases I (ii) but if A is released during a flash period I (ii) holds to the flash battery and maintains B which is necessary since the distant apparatus does not commence to release until the termination of the flash period. Faults. If switch DS is accidentally moved to an even numbered contact at a time when B is operated and C is released, M pulls up and holds B to cause a lock-up and light the alarm lamp AL. Routine testing and statistical metering. Wires S, T, U, V, W, X, are connected to the access switch of the toutiner which operates R to disconnect the outgoing junction. A statistical meter CM is operated over contacts of E, H when the booster impulse is received from the register translator at the termination of sending.