Patent GB-718438-A (GB)
Title: Improvements in or relating to circuit arrangements for telephone installations
IPC: H04Q3/00
Filed: 1951-10-31
Abstract: 718,438. Automatic exchange systems. SIEMENS & HALSKE AKT.-GES. Oct. 31, 1951, [Dec. 20, 1950], No. 25507/51. Class 40 (4). In a network of exchanges divided into zones each comprising a zone exchange ZA, Fig. 1, denoted by a first code digit A, secondary exchanges HA denoted by digits A, B and tertiary exchanges KA denoted by digits A, B, C and satellites EA of these exchanges, the code digits are stored in the first zone, secondary or tertiary exchange reached in setting up the connection and are repeated in response to signals from each succeeding exchange reached to control alternative routing, the signals determining how many of the code digits are to be repeated. Tie lines QK, QH, QZ are provided between the zone, secondary and tertiary exchanges of different zones and are connected in sequence in the banks of the selectors so that the possible routes are searched in the order of their directness, the normal route to the associated higher grade exchange in the same zone being searched last. The remaining digits are sent from the exchange storing the code digits when no further backward signals are received. The digits may be transmitted as impulses of a voice frequency. Setting up a connection from tertiary exchange KA262 to subscriber 3624357. The digits incoming from a subscriber of the exchange KA262 or of an associated satellite EA are repeated by relay A, the code digits 362 being registered in turn on switches D1, D2, Dg and the remaining digits 4357 being stored in a mechanical impulse regenerator IW. A marking switch M in response to the first and second code digits marks the tie line groups QK3, QK2, and with the help of wiper Dgl marks QK1. Relays W (not shown) and H operate, the latter being the start relay of the group selector UW. The wanted subscriber is connected to a satellite EA3624 of the tertiary exchange KA362. The group selector in turn searches across the tie line groups QK1, QK2, QK3 leading to the tertiary, secondary and zone exchanges, respectively, associated with the wanted subscriber and then searches the normal route RL to the secondary exchange HA26. At each of contacts R1, R2, R3 positioned between the groups the selector UW temporarily completes a circuit for Q which energizes the forward magnet Smv of a switch sm which makes one forward step. If a free tie line QK1 is found, W releases slowly whereupon the impulse regenerator IW sends the remaining digits 4357 by means of contact nsi. If tie lines QK2 or QK3 are used one or two code digits are sent to set the selectors in exchanges HA36 or ZA3 and HA36, respectively, to the tertiary exchange KA 362. In the last case the switch sm is on outlet 2 and when W releases a switch magnet Da and an impulsing relay I interact until 6 impulses have been sent, a circuit then being closed over switches D2, Da for a relay T which energizes the reverse magnet Smr to move the switch sm one step back. Switch Da returns to normal. The digit 2 is sent after which T again reverses the switch sm which over its normal contact connects up the impulse regenerator IW. If no tie lines are found the normal route RL to the secondary exchange HA 26 is seized and all three code digits are repeated. At the secondary exchange HA26 the code digits are registered on switches Dml, Dm2, which mark the outgoing group. selector UW to hunt in sequence over tie line outlet groups QH1, QH2, QH3 and the normal route outlets RL. Each time the selector passes from one to another of the groups QB reverts a negative pulse. At the exchange KA262, RS responds to the negative pulses to step switch sm and to energize W. Should an idle tie line be found the number of code digits determined by the switch sm are transmitted from the exchange KA262 when W releases, and the numerical digits follow. Otherwise the normal route RL to the zone exchange ZA2 is seized and all the code digits are repeated from KA262. The first code digit 3 sets an incoming group selector ZGW and the other two are registered on switches Dm3, Dm4, which mark the outgoing group selector UW. Tie line groups QZ1, QZ2 to the tertiary and secondary exchanges KA362, HA36, respectively, and normal routes RL, RL2-4 to the zone exchanges ZA3, ZA4 are searched sequentially, and negative pulses are reverted by QC to set the switch sm at the exchange KA262. If no other route is available the call is set up via zone exchanges ZA4, ZA3. Metering.-The marking switch M and digit switch Dg in exchange KA262 prepare a circuit for the appropriate one of a number of metering pulse contacts z1 ... z4 which actuate periodically at different rates.