GB554136A - Improvements in or relating to telephone systems - Google Patents

Abstract

554,136. Automatic exchange systems. AUTOMATIC TELEPHONE & ELECTRIC CO., Ltd., PEARCE, O. A., and OLIVER, S. H. Dec. 18, 1941, No. 16334. [Class 40 (iv)] In an automatic P.B.X., local calls are established over finder-connector links and main exchange calls over a separate set of finders connected individually to junctions, one of these being started in search of a subscriber's line when the latter has both its line and its cut-off relay actuated. This arrangement facilitates the transfer of main exchange calls and, as described in Specification 554,137, the extension of calls incoming over a particular junction to a particular subscriber at night. Local calls.-Line relay R completes a starting circuit for a link allotted by apparatus 10 and marks the line calling. When the line is found, T stops the finder and switching relay HA pulls up in series with cut-off relay K and is followed by line and release relays A, B. The call is completed over a connector CS. Outgoing main-office calls.-The connector is set by the digit O and in this position grounds finder wiper LFS4 to re-operate the line relay R. Since K is still up, this completes marking and starting circuits for the finder EFS of a junction and when the latter switches through, earth on wiper EFS4 shunts down HA to free the local link. Transferring main-office call.-A substation push button (not shown) is operated to hold the main office and take into use transfer equipment (not shown) which takes into use a local link over'which the third party is called as described in Specification 389,867. If he accepts the transfer, the original local party hangs up and on the release of B, transfer relay TR (not shown) being operated, a circuit is made over connector wiper CS4 for the line relay of the third party whereupon the finder of the junction hunts for his line. Incoming calls.-No details are shown. It is suggested that an incoming call might ring a common bell, switch over the test relay of the finder EFS concerned to an additional bank (not shown) and so modify the starting circuits that the removal of his handset by any subscriber would cause the switch EFS to connect with his line. According to an alternative suggestion, an incoming call would ground the wiper LFS4 in the allotted local link so that the call would be completed in the manner described above for an outgoing call.