Patent GB-555638-A (GB)
Title: Improvements in or relating to circuit controlling apparatus, and telephone systems including such apparatus
IPC: H01H67/26
Filed: 1941-12-01
Abstract: 555,638. Automatic exchange systems. STEVENS, A. H. (Kellogg Switchboard & Supply Co.). Dec. 1, 1941, No. 15481. [Class 40 (iv)] A selecting device which acts as a number of finder-connector links comprises a number of relays O each of which comprises a number of spring sets a1 ... a10, the set to be operative being selected by rotating a cam shaft 16 common to all the relays step-by-step to tilt one of a number of members 14 on a plate 10 carried by a common operating bar into operative association with its spring-set, the plate 10 having been previously moved endwise relatively to the bar by a magnet individual to a relay. After selection for one relay has been completed, the cam shaft is restored, the member 14 being held in its tilted position by an insulating stud on the contact spring. The shaft can then be used for the control of another relay. Shaft 16 also controls the operation in succession of a number of contact springs by means of cams (not shown). Operation as call-finder.-When subscriber 1 calls, his line relay 110 marks the line calling by removing ground from the corresponding one of a series of contacts 114 (shown as terminals co-operating with a wiper but actually constituted by springs controlled by cams) and energizes 103 which energizes driving magnet M of shaft 16. Off-normal springs ON energize relay 102 which releases 103 and changes the circuit of M to one including self-interrupting contacts 124 and the group of contacts 114. Stepping therefore continues until the calling contact is found whereupon the magnet is unable to reoperate and 102, which since the release of 103 has been held over contacts 114 falls back. On the operation of 102, relay 101 pulled up to energize shift relay SR 1  which energized shift magnet S<SP>1</SP> (assuming the contact group A to be idle) which shifted plate 10a and closed contact 46a. Consequently, when 102 falls, there is a circuit for O<SP>1</SP> which operates the selected contacts and the contacts 161 and changes over contact 163 to ensure operation of SR<SP>2</SP> instead of SR 1  on a subsequent call. Relay 201 and cut-off relay 111 now operate on series, 110, 101 fall back, and 202 pulls up over the loop and energizes 203 and 104 the latter energizing 105. Operation as final selector.-On the relapse of 101, magnet M is reoperated in a selfinterrupting circuit until the shaft 16 reaches normal. When SR 1  fell it released S<SP>1</SP> but O<SP>1</SP> was held by 201. 204 now connects up dial tone. Dialled impulses are repeated by 202 to 104 which repeats them to magnet M. At the end of the digit, 106 pulls up over off-normal contacts and, since SR<SP>3</SP> energized shift magnet S3 on the operation of 105, there is now a circuit for magnet O<SP>3</SP> which operates the selected contact set locks up and connects 206, 210 to the cut-off relay 149 of the wanted line. 206 pulls up and, if the line is idle, 210 also pulls up and energizes 211 which locks. 206 energizes 212 which sends back busy tone if 210, 211 fail to come up. If the line is idle however, ringing current interrupted by relay 209 is fed to the line over relay 208. When the called party replies, 208 releases 210 and 207 pulls up over the called loop and makes an alternative circuit for 211. On the operation of 212, 204 is released followed by 104, 105 and a circuit is thus made for restoring the selecting mechanism. When the calling party hangs up, feed relay 202 falls followed by 203 and when the called party hangs up, 207 falls back. On the relapse of 203, 205 comes up and releases 201 which releases O<SP>1</SP> and when 207 falls back 211 falls and releases O<SP>3</SP> whereupon 205 falls again. Simultaneous calls.-If a second call is made while the first is being established, the release of 204, 104, 105 when the magnet O at the calling end of the link is operated enables the selecting shaft to go round again under control of the new call.