Patent GB-191413173-A (GB)
Title: Improvements in Automatic Telephone Exchange Connexions.
Filed: 1914-05-28
Granted: 1915-05-28
Abstract: 13,173. Betulander Automatic Telephone Co., Bryant, G. H. and Ward, F. M. May 28. Automatic exchange systems.-The shaft and wipers of a connector are arranged to drop over groups of terminals, ten at a time, in response to the tens digit impulses, and to rise step by step over the terminals of the selected group in response to the units impulses. In the arrangement described, each connector is associated with a call-finder of the gravity type described in Specification 6465/13. Construction of connector. This is a modification of the construction. described in Specification 19,553/11, the tilting-magnet T<II> being provided with a catch P<II> co-operating with teeth T<o> on the shaft, so that in addition to keeping the wipers B<III>, B<IV> clear of the line terminals during the setting of the switch, it also serves to control the first or dropping adjustment. The upward stepping-movement is effected by a. magnet M<II>, which operates a pawl engaging with ratchet teeth on the shaft. The energization of the magnet is, however, ineffective unless an auxiliary magnet A<II> is energized at the same time to move a detent into engagement with the ratchet teeth. Call-finder. When a calling subscriber X lifts down his telephone, his line relay L completes a starting-circuit 50 (or sets in action a searcher such as is described in Specifications 18,076/14 and 18,154/14) to energize the magnets M<1>, T<1> of the first idle finder, the shaft of which is thereby released and carries the wipers W<I>, B<I>, B<II> over the terminals CP, TW. The test terminals of non-calling lines and of lines to which a connexion has already been made are grounded, and the magnets M<I>, T<I> are therefore kept energized over the test wiper W<I> (their original circuit having been opened by the off-normal switch SS) until the calling line is reached, whereupon they de-energize and bring the finder to a stop. The de-energization of the relay T' connects ground to the test terminals CP, WP of the calling line and energizes the cut-off relay CO, which disconnects the relay L from line and locks it in a local circuit. Connector. The de-energization of the magnet T<I> also allows the wipers B<I>, B<II> to engage the terminals TW of the calling line, which energizes the connector line relay T<r>, and the slow-release relay G. The calling line is now interrupted a number of times representing the tens digit of the wanted subscriber's number, and at each interruption, the relay T<r> deenergizes'and completes a circuit through its lower armature for the magnet T<II>, which drops the shaft and its wipers over ten sets of terminals. During this operation, the magnet M<II> is energized (for the purpose of retracting its pawl, which would otherwise prevent the shaft from dropping) by a slow-release relay D, which is energized at the first impulse by a circuit through the upper spring of the off-normal switch RS and locks itself through the middle spring. At the conclusion of the tens impulses, the relay T<r> remains energized, and the relay D has time to de-energize. In response to the second or units set of impulses, the relay D does not become energized, its original circuit being now open at the top spring of the switch RS, but a slow-release relay R is energized instead, and this relay energizes the auxiliary magnet A<II>, which energizes also the tilting- magnet T<II>. The impulses of this series are forwarded through the lower armatures of the relays T<r>, G, D to the magnet M<II>, which steps up the shaft and wipers to the terminals of the wanted line. Busy test and signal; supply of ringing- current. If this line is already engaged, i.e. if there is ground potential on the test terminal WP, the relay T<II> remains energized over the test wiper W<II> and connects a busy-tone circuit to the calling line. If, however, the wanted line is idle, the relay T<II> de-energizes along with the relay R and magnet A<II>, permitting the wipers B<III>, B<IV> to engage the selected line terminals, and connecting the test wiper W<II> to ground. Ringing-current is now supplied. When the call is answered, a ringing cut-off relay S in the ringing-current responds to the increased current and completes the talking- circuit, at the same time locking itself in series with the relay G by opening a short circuit across its upper winding. The called line is now supplied with current through a relay F. Release. The connector can be released by either subscriber, but the call-finder can only be restored by the calling subscriber. The deenergization of either of the line relays T<r>, F energizes the relay R, which energizes the magnets A<II>, T<II> and completes a circuit from the interrupter I<I> through the stepping-magnet M<II>, this circuit and that of the relay R being opened by the switch RS when the connector regains its normal position. The de-energization of the relay G, controlled by the line relay T<r>, energizes the magnets A<I>, T<I> and completes a circuit from the interrupter I<III> through the stepping- magnet M<I>, this circuit and that of the magnet AI being opened by the switch SS when the call-finder regains its normal position.