Patent GB-334578-A (GB)
Title: Improvements in or relating to telephone systems
IPC: H04Q3/00
Filed: 1929-06-05
Abstract: 334,578. Standard Telephones & Cables, Ltd., and Wright, E. P. G. June 5, 1929. Automatic and semi-automatic exchange systems.-In a system employing common registermarkers, the selection of a wanted outlet or group of outlets at a switching stage is in part determined by common discriminating means operated by a signal additional to the digit or digits transmitted to the stage. In one application to a bypath system described only with reference to the lay-out shown in Fig. 1, a switching stage 2A may be reached over either of different stages 1A, 1B, and consequently, the digit or digits dialled into 2A may be identical for different lines reached thereover. A relay A in the, bypath circuit is operated with or without operation of relay D in accordance with the route of access, and relay D changes the connections between marking and by-path switches R1, R2. In the by-path system shown in Fig. 2 and fully described with reference to Figs. 3 and 4, connections are set up over a group selecting stage S and a final stage comprising two different groups of switches SA1, SA2 associated with the same by-path circuit FBP. These stages deal with calls in two thousand-groups comprising only two hundred-groups, or two hundred members distributed in more than two hundredgroups, in each thousand-group. Discrimination in accordance with the thousands group is effected by relay JJ in the by-path circuit at stage S, JJ being operated or not in accordance with a key operation by an. operator or the route of access from a preceding stage, in order tu change the marking connections between switches R1 R2. Switch R1 is set by the hundreds digit, and R2 chases and hunts for an idle outlet in group SA1 or SA2 depending on the digit. If the outlet is in group SA2, the group selector by-path circuit sends a signal to the final by-path circuit to operate JJA which connects up corresponding wipers of RA2. The switches SAI, SA2 are 50 point double-wiper switches and RA2 is a 50 point switch with four test wipers, one or other of the pairs being connected up dependent on JJA while the connection of the wipers in each pair is dependent on the value of the tens digit, JA being operated if this digit is odd. Group selector, Fig. 3. An idle trunk associated with an idle by-path circuit has battery on normal contact of wiper K of R2 connected over normal contacts of wipers 8 and 6 of R1 and contacts of relays individual to the trunk to conductor T. When the trunk is seized by an operator, relay A is operated alone or in series with JJ in accordance with a key operation which completes a circuit from BP + to BP - or to 2BP. Relay B pulls up and operates TB which grounds the test wire T. The impulses are repeated to R1 over relay C and when R1 has taken one step, R2 takes a step over m1, h2, wiper N of R2, wiper 5 of R1 to ground at b2 and continues stepping over N, q1, p1. The first contacts of the groups in bank C of R2 are wired to the second and subsequent contacts in banks 9 and 10 of R1, so that with JJ unoperated R2 hunts until M operates over 10. On the relapse of relay C, E pulls up over off-normal bank N, locks up, releases M and connects up test relays P, Q so that R2 hunts for an idle final bypath circuit and selector in the marked group, while R1 hunts for the conversational switch taken into use by the operator. When R2 finds an idle outlet over T1 or T2, P, or Q, and J pull up followed by H which connects ground from tb5 to T1 or T2 and disconnects P and Q therefrom. The conversational switch is a double wiper 50-point switch serving 100 outlets and relay J connects up the second set of marking, test and impulse circuit wipers M2, T2, I2, of R2 if an idle outlet over T2 is found. If T1, T2 find idle outlets simultaneously, both P and Q pull up but J remains inert. When R1 finds the conversational switch, T operates to ground on wire H, locks up and releases TB which extinguishes a supervisory lamp at the operating position or releases the previous by-path circuit if one is used, and also completes a stepping circuit over wiper 5 of Rl for magnet S of the conversational switch which is opened when relay M operates over M1 or M2, wiper M of S and wiper 10 of R1. Relay GS operates over wiper 6 of R1 to connect up continuous ringing lead CR without effect at present. If JJ is energized, it locks over its lower winding, short circuits its upper winding to prevent impulse distortion and replaces wiper 10 of R1 by wiper 9 so that R2 is, in response to the setting of R1 in accordance with the first digit, moved to a different group of contacts. All outlets busy. Relay M operates over last terminals of the group to ground at e8 and completes a circuit for G over off-normal bank N to ground over p1, q1. Relay G is of high resistance and slow-to-operate so that P and Q may operate if the last terminals are idle. When TB relapses as described in the preceding paragraph, BS pulls up over wiper 7 of R1, and connects the calling loop to AS which locks BS and connects up tone from BT. Final selector, Fig. 4. An idle by-path and selector combination has battery over wipers X1 of RA2 and 8 of RA1 connected to the test conductor and when it is seized, impulse relay AA operates alone or in series with JJA according to the group containing the seized final selector, contacts of banks 11, 12, Fig. 3, being multiplied direct to AA in one case and over JJ in the second case. Relay BA pulls up and the third digit is repeated over CA to magnet RA1.The pairs of contacts 1 and 2, 3 and 4, and so on in the first part of the bank of wiper 9 of RA1 are connected to contacts preceding the) groups in the bank of wiper C of RA2, and RA2 steps in a circuit including the first off-normal arc in bank 3 of RA1 until MA operates over wipers C and 9 and opens the drive. Relay CA falls back at the end of the digit, completes a circuit over wiper 4 of RA1 for relay GA which locks up and completes a stepping circuit for RA1 first over wiper 4 and subsequently, when MA has released owing to movement of RA1, over wiper 3, in which RA1 moves to position 12 and waits for the units digit. If the tens digit is odd JA operates over wiper 8, holds first over ga9 and subsequently over ea8, and determines in conjunction with JJA which of the test wipers is connected up. The group contacts in the bank of wiper C are multiplied to a group of contacts commencing at 13 in the bank of wiper 9. The units digit is repeated to RA1 .and when CA relapses at the end of the train RA2 steps in a circuit including the second offnormal arc of wiper 3 of RA1 until MA operates over wipers C and 9, opens the drive, and operates EA over wiper 4 which opens the circuit of GA. Busy test and signal. Relay GA is slow-torelease and in the meantime the test circuit. is completed over PA and wiper 8 of RA1. If the line is busy, PA fails to operate, and GA opens the by-path test circuit so that E, Fig. 3, falls back and operates BS over wiper 7 of R1. Relay BS operates AS which applies busy tone as before and releases A and B, and therefore the by-path circuits. When switch R1 had stepped on to the group selector a relay at the operator's position opened the original circuit of A so that this relay remained held over the incoming speaking wires. If the line is free, PA pulls up and energizes HA which holds E, Fig. 3. Completion of connection; ringing. Relay HA releases MA and RA1 hunts for the seized final selector, the driving circuit being opened when TA operates over wiper 1 of RA1 wiper H of the group selector to ground at gs5. Relay TA locks up and closes a stepping circuit for final selector SA over wiper 16 of RA1 which is opened when MA operates over M1 or M2, wiper M of the final selector and wiper 9 of RA1. Relay HS operates over wiper 5 and switches through so that continuous ringing from CR in the group selector is connected to line. HS locks up over hs2 and wiper H of SA to ground connected by HA over PA to the test wiper of RA2, this ground being extended over hs1 to wiper H of the group selector. The by-path test. conductor is opened at hs5 and relay E in the preceding by-path circuit falls back and releases GS, continuous ring- ing being applied during the release period of this relay. On the relapse of GS, BS pulls up over wiper 7 of R1 and connects the calling loop to AS which re-operates GS over wipers H of the group selector and 8, 6 of R1. Relay GS locks to as4 and completes the interrupted ringing circuit over relay FS which, when the called party replies, trips the ringing, locks up, and connects up the answering supervisory relay DS. P.B.X. arrangements. Provision is made for 50 P.B.X. lines in each hundreds group, JJ determining which of the P.B.X. test wipers X1, X2 is connected; JA is operated. If the called line is the first of a P.B.X. group, VA is operated by battery over X1 or X2, locks, up and releases MA which recloses the stepping circuit of RA2 over wiper 3 of RA1, GA being maintained operated in parallel. If an idle line is found, PA operates and the connection is completed as described in the preceding paragraph. If all the lines are busy, MA operates to ground over X1 or X2, opens the stepping circuit of RA2 and releases GA with results as previously described If a line other than the first, in the group is called, VA does not operate and this line only will be tested. Standstill release. If the tens digit does not come into the final by-path circuit due to a fault or failure to dial, relay VA is operated by a ground pulse over A and wiper 7 (normal) of RA1 and locks over wiper 3. A subsequent pulse over Z operates EA which opens the by-path test circuit so that E in the preceding by-path falls back and BS pulls up to send busy tone and release the penultimate and final by-paths. Relay VA is similarly operated in position 12 of RA1 if the units digit does not come in. Similar pulse circuits are associ