Patent GB-343978-A (GB)
Title: Improvements relating to automatic telephone systems
IPC: H04Q3/42
Filed: 1929-11-27
Abstract: 343,978. Automatic exchange systems. SIEMENS BROS. & CO., Ltd., Caxton House, Tothill Street, and PETERS, C. L., 21, Croft Villas, Green Lane, Eltham, both in London. Nov. 27, 1929, No. 36329. [Class 40 (iv).] In an office in which finder-connector links with common control circuits are used, the connectors give access to all the lines, the finders only to groups of lines. In the 200-line system described a call starts the assigner AS2 or AS3 which causes the switch CCF of an idle control circuit RCE to seize an idle link CC of the appropriate group. The assigner circuit is identical with that described in Specification 332,904, [Class 40 (iv), Telephones &c.], and the link circuit differs only in that the connector is of double-wiper type and has special arrangements for giving access to junctions. The control circuit is, except as will be apparent from the detailed description below, identical with that described in Specification 334,524, [Class 40 (iv), Telephones &c.]. Other features of the system are claimed in Specification 343,611. Specifications 203,759, 314,313, [both in Class 40 (iv), Telephones &c.], and 343,674 also are referred to. Selection of local subscriber. Starting relay ST or STT in the control circuit, depending on which assigner seized it, renders the test circuit for CCA effective only for the proper group of connecting circuits and connects up LS2 or LS3 of the switch LS which sends the vertical digit to the call finder. An additional winding (iii) causes impulse relay A to pull up when M opens the vertical stepping circuit to prevent a possible false impulse to the connector. When the line is found A holds over its other windings and the loop, M being released, and repeats the digits to the connector magnets and to the register magnets DSA, DSB. If the 1st digit is 2 or 3, indicating a local call, a circuit is made for the release magnet ZMM over the vertical wiper VC. If the digit is 3, S also is operated to change the wiper set. The sequence switch which moved off normal when V pulled up moves two steps per digit as described in Specification 334,524. The tens and units digits operate the connector and the registers DSA, DSB, DSA not being restored after the 1st digit. If the line is the first of a group to a P.B.X. hunting proceeds as described in Specification 334,524, DSA2 or DSA3 being connected up by CO according as the 1st digit was 2 or 3. Connections to ordinary and party lines are controlled as in the prior system. Reverting calls are made by dialling a single digit (7) and then ringing with the hand generator. DSA energizes RL to release the control circuit and the line is locked away from the exchange apparatus as described in Specification 314,313. Calls to junctions by dialling 0 only or 9 followed by another digit. All the junctions are in the 200 group. DR is connected to all the terminals in DSA6 corresponding to junctions outgoing from the top level of the connector except the last, and when 0 is dialled JT pulls up and DR energizes G and starts the interrupters so that DSA and the connector are stepped synchronously until an idle junction is found (when P pulls up) or the end of the group is reached. The junction is rung like an ordinary line. If 9 is dialled, JN is operated as well as JT to connect up DSA7 the terminals of which are connected to DR in a manner corresponding to the arrangement of junctions in level 9 of the connector. With JN operated, a circuit is made over which the sequence switch races to its 7th terminals. DSA and the rotary magnet of the connector now respond to the 2nd digit, the sequence switch moving on to its 9th terminals to energize DR. Hunting then proceeds in the selected group in the same way as in the 10th level. With JT operated, metering is prevented. Release in junction calls. When the calling party hangs up, PP is short-circuited and VY (which in local calls delays release until the called party clears) falls and releases the connector. Trunk offering. Incoming junctions are associated with connecting and control circuits in the same way as subscribers' lines. Their metering terminals however are connected to battery so that when the junction is found, JC pulls up and locks itself. If the operator wishes to break in on a busy line she dials an extra digit which if the line is a party line must be that for selecting the required ringing code but otherwise may have any value. The sequence switch goes to 9 in which N is operated, cuts off the busy tone and makes a new circuit for G, and a speaking circuit. When the local call has been cleared P releases G and the line is rung as in a normal call. This part of the system is claimed in Specification 343,611. Maintenance from distant office. If a subscriber dials 1, 4, 5, 6 or 8 as a first digit, L is operated, NU tone is sent back and further control of the circuits is prevented. If however 1 is dialled by a distant operator N is operated instead of L and the operator may dial a second digit whereby she may ascertain by means of tones over DSA4 whether there are any faults in the office or whether the battery is being charged or may stop or start charging. Testing and statistical metering. The assigner has a test jack which causes it to go home. The control circuit has a test jack TJ over which ST or STT and AT are operated and the 9th terminal of LS4 is marked. CCA moves to its 1st terminals and is there stopped by TT. LS drives to its 9th terminals and then operates M. A routine tester connected over the 1st terminals of CCA, CCB then takes charge. A statistical meter may be connected at TM for operation by the metering relay MR.