Patent GB-857023-A (GB)
Title: Improvements relating to automatic telephone systems
Inventor: WARMAN BLOOMFIELD JAMES
IPC: H04Q3/00
Filed: 1956-07-09
Abstract: 857,023. Automatic - exchange systems. SIEMENS EDISON SWAN Ltd. July 4, 1957 [July 9, 1956], No. 21197/56. Class 40 (4). In a final selector switch a group of PBX outlets is preceded by a first control outlet and followed by a second control outlet such that when the switch is set on a first control outlet a control circuit which is available to a number of final selector switches is seized and initiates and controls hunting over the group and if there is no free outlet the second control contact is reached and causes the control circuit to relinquish the search. The invention is applied to an exchange in which high-speed motor uniselectors are used and calls between local subscribers are set up under the control of a register controller. Selectors are set to a required outlet by comparing the digits stored in the register with the number of impulses reverted by a selector as it drives round from a normal position. As illustrated in Fig. 1, a final selector has wiper sets SW1-SW8 each set having two wipers displaced by 180 degrees and each sweeping its own contact bank. The outlets of wipers SW1, SW5, SW7 (which will be called the upper outlets) are connected to the inlet when relay WS is not energized and the outlets of wipers SW2, SW6, SW8 (the lower outlets) are connected to the inlets when SW is energized. All PBX groups must terminate in the lower outlets but may begin in either upper or lower outlets. If a PBX group begins in the lower outlets it is preceded by an outlet of wiper SW6 connected to terminal T3 and the corresponding outlet of wiper SW4 connected to terminal T1. If the PBX group begins in the upper outlets it is preceded by an outlet of wiper SW5 connected to terminal T3 and by the corresponding outlet of wiper SW4 connected to terminal T2. The end of the group is always marked by an outlet of wiper SW4 connected to terminal T1. The outlet marking the end of a group may also serve as the outlet marking the beginning of another group. In its normal condition the final selector connects negative battery to the positive and negative incoming wires and to the incoming private wire P. Outlets of the selector are to relay less line circuits which have their P-wire normally at from - 5 to - 10 volts depending on leakage but when busy the voltage rises to earth. In Fig. 2 is shown the one of a number of control circuits which it is assumed is the one taken into use by the final selector of Fig. 1. Common to all terminals T3 is a start relay ST which starts a motor uniselector CW in search of the final selector. Call to an ordinary subscriber's line.-Earth on the P-wire busys the final selector against intrusion and if an outlet in the lower outlets is required the register controller puts earth on the incoming negative wire to operate WS. Earth on the incoming positive wire energizes the latch magnet SLM and starts the switch motor. In rotating from normal the switch sends back impulses from wipers SW3 which are counted by the register controller to halt the switch on the required outlet by removing earth from the positive wire. The outlet is tested by the register controller over the P-wire and supervision by way of ring or busy tone is then vested in the first group selector while the register controller goes free. Call to PBX group assuming that the group is wholly in the lower outlets.-The final selector is set by the register controller on to the control outlet preceding the wanted PBX group with relay WS operated. On relapse of latch magnet SLM relay ST operates over wiper SW6 to earth in the register controller and in series with a discriminating relay at the register controller. ST starts the control circuit of Fig. 2 by energizing the latch magnet LM so that the switch drives round until wiper CW6 encounters negative battery in the circuit of magnet SLM and wiper SW4 over the first control outlet, relay TA responding in the control circuit to halt switch CW by energizing relay H in series with the latch magnet. With H operated latch magnet SLM is re-energized by virtue of a loop circuit over wipers CW2, CW3, and earth from off normal contact ONS2. The earth which energizes SLM causes relay TA to fall back in the control circuit and over its back contact TA energizes HS which locks up with relay HM over wipers CW6 and SW4. The earth energizing SLM is also applied to the incoming positive wire to disable the discriminating relay at the register controller and cause it to initiate the timing of a half second interval limiting the duration for which the controller is in service for the call. When the final selector is driven off its first control outlet HS is released with ST. An idle line of the group is marked by negative battery on the P- wire and, over wipers SW8, CW7, drives transistor TSR to conduction to operate test relay TC. The contact of TC breaks the earth loop energizing SLM and thereby halts the final selectors; it also energizes HAS and HBS in parallel, HBS coming up slowly. When HBS is operated it releases H and consequently the whole control circuit which homes to normal. When the half second interval expires at the register controller this circuit is released and control is bequeathed to the first group selector. At the end of a call the final selector homes to normal under the control of a common homing circuit associated with terminals T4 to T8. To enable the selector to home in spite of the fact that the selector is standing on a busy outlet rectifiers MR1, MR2 are used in the P-wire connection. If there is no idle line in the group the final selector drives on to the second control outlet which over wiper SW4 causes relay HA to respond in the control circuit and disconnects the test relay TC so that the final selector drives home to its normal position. HA also energizes HAS and when the final selector reaches its normal position contacts ONS2 break the energizing circuit of SLM but connect up the on normal relay ON in the control circuit. ON energizes HBS which is slow to operate and before it does so releases WS by earth over wiper CW1. While WS falls back ON connects positive battery to the incoming negative wire over wiper CW4 and thereby releases the register controller and returns busy tone from the first group selector. Call to a PBX group with group in upper and lower outlets.-If a free outlet exists in the earlier part of the group in the upper outlets the control circuit behaves as described for a group in the lower outlets. If there is no free outlet among the upper outlets the final selector is driven to normal where contacts ONS2 open causing ON to respond and, since only relays H and HM are operated, when ON operates it energizes WS with earth over wiper CW5. ON also energizes slow to operate relay HBS. WS puts positive battery on the incoming positive wire to reoperate the discriminating relay at the register controller and ensure that when the final selector drives into the remaining part of the group the controller will set off with a fresh half-second service interval. When HBS finally operates it disables ON which disables HBS and the control circuit proceeds as before.