GB240605A - Improvements in automatic and semi automatic telephone systems - Google Patents

Abstract

240,605. Western Electric Co., Ltd., (Western Electric Co., Inc.). Aug. 19, 1924. Automatic exchange systems.-A switch having two or more sets of wipers is so arranged that the number of sets effective during the hunting operation of the switch is dependent upon the level to which the switch shaft has been raised. Thus, in the group selector shown, the digit 5 causes both sets of wipers 30 - - 32, 33 - - 35 to hunt and test simultaneously over the fifth and third levels respectively, whilst in response to the digit O hunting takes place over the tenth level only, the lower set of wipers being ineffective. The invention is stated to be applicable also to group selectors provided with arrangements for an eleventh rotary step, and to connectors. Simultaneous hunting over two levels. The five impulses of the first digit are repeated in the usual manner by the line relay IR to the vertical magnet VM in series with relay C which operates the stepping relay E over off-normal contacts S1. Relay E locks up over contacts 49 of the rotary magnet RM and energizes relay F. Upon the relapse of relay C at the end of the digit, the rotary magnet RM rotates the wipers one step and unlocks relay E. If both wipers 32, 35 engage earthed busy terminals, relay E energizes again over contacts 51, 49, 8 and wiper 35, and relay F remains energized over contacts 77, 11, and wiper 32, so that the wipers take a further step and rotation continues until one or other set of wipers find an idle trunk. Suppose now that wiper 35 reaches an idle terminal 65 at the same time that wiper 32 engages a busy terminal 62. Relay F remains energized over wiper 32, but the absence of earth on wiper 35 prevents the operation of relay E and causes the switching relay D to energize in series therewith to extend the connection. Relay F remains locked up throughout the conversation over contacts 77, 10, 8 and lead 78 earthed by a succeeding switch. If, alternatively, terminal 62 is idle when reached by wiper 32, relay F de-energizes as soon as relay E releases, relay D being. no longer short-circuited over lead 78 energizes and the connection is extended over wipers 30 - - 32. Hunting over a single level. In response to the digit 0, an auxiliary vertical wiper 36 engages a grounded terminal 55 so that a relay Z is energized to disconnect relay F. Wipers 33 - - 35 are thus isolated and hunting takes place in the usual manner over the tenth level only under the joint control of rotary magnet RM, stepping relay E, and test wiper 32. Alternatively, instead of the extra wiper 36 and relay F, relay F might be controlled directly by shaft springs.