Patent GB-191411212-A (GB)
Title: Improved Circuit Arrangements for Telephone Exchanges.
Filed: 1914-05-06
Granted: 1915-07-22
Abstract: 11,212. Siemens Bros. & Co., [Siemens & Halske Akt. - Ges.]. May 6. [Addition to 27,458/09 and 18,356/12.] Semi-automatic exchange systems.-In systems in which calling lines are connected to operator's positions through two call-finders in succession, the primary finder is not taken into use unless it is itself idle, and has access to an idle operator's position. The arrangement may also be such that the primary finder is marked busy if the secondary finders to which it has access are in use, as described in the parent Specification. The invention is described as applied to a semi-automatic system in which calling lines 1, 2, 3 ... 1999 are connected through first and second pre-selectors IVW, IIVW to selector trunks VLI ... VLV, from which lateral connexions are made through call-finders IAS, IIAS to operators' positions. The operators' positions are divided into groups, three groups being shown at A, B, C, and each group consisting of three positions as shown at API, APII, APIII for group A. Each position has three impulsesenders ZG1, ZG2, ZG3, &c., each associated with a secondary call-finder IIAS. The primary callfinders IAS serving the first group of selector trunks are so arranged that the first such callfinder IASIa is allotted to the first group of positions A, the second finder IASIbto the second group of positions B, the third finder IASIc to the third group C, and so on. When a call comes in over one of the selector trunks VLI, the selection of a primary finder IASI to find the call is effected by a distributing-switch WS, the leads from which test busy if (1) the off-normal contact 2 is closed by the taking into use of the finder, or (2) all the operators in one group of positions are busy, contacts 3, 4, 5 being closed by their speaking-keys. Thus, if the first primary finder IASIa is in use, or if all the operators at position A are busy, the switch WS selects the primary finder IASIb accessible from the group of positions B, or if this finder is in use, or all the operators in the B group are busy, the switch WS selects the primary finder IASIc in group C. If, however, all the operators in all the groups of positions A, B, C are busy, contacts 6, 7, 8, 9, 10 controlled by their speaking-keys close the circuit of a relay Q, which, by opening contacts 13, 14, disconnects the leads containing contacts such as 3, 4, 5, so that the switch WS then selects the first free primary finder, irrespective of whether it has access to an idle position or not. The selection of a secondary finder to handle a call incoming in a certain group of operators' positions is effected by a distributing- switch WS<1>, the three arms 15, 26, 27 of which may be connected by an auxiliary switch S to a relay E controlling the motor magnet D3 of the switch WS'. The leads from the contacts engaged by arm 15 of the switch WS' include contacts such as 16, 17, of which the contact 17 is opened by the relay F1 when the finder is taken into use, and the contact 16 is opened when the speaking-key of the operator API is depressed. The first secondary finders IIAS1, HAS<1>1, IIAS<11>1 of the three operators' positions API, APII, APIII are thus marked busy, either if they are in use or if the associated operator is engaged. If, however, all the operators in any one group of positions A are engaged, contacts controlled by their speaking-keys and arranged in series in the lead L1 energize relays R1, R2, R3 at each operator's position, thus shunting the contacts 16, 16<1>, 16<11>, so that the first idle one of the first secondary finders IIAS1, IIAS<1>1, IIAS<11>1 is taken into use, even although the associated operator is busy. Incoming calls are thus connected by first secondary finders to idle operators until all the operators are engaged, and then by first secondary finders to the positions of engaged operators until all the first secondary finders are in use. When this occurs, contacts 22, 23, 24 in a lead G, are all closed and energize a relay PV, which causes the motor magnet DV to rotate the switch S through one step, thereby connecting the relay E to the arm 26 of the distributing-switch WS<1>. As further calls are received, the switch WS<1> rotates until its arm 26 finds idle second secondary finders HAS2, HAS<1>2, and when all these are in use, contacts 36, 37 again complete the circuit of the relay PV, moving the switch S into its next position, in which the arm 27 is connected to the relay E so that further calls are handled by third secondary finders IIAS3, IIAS<1>3. Instead of arranging that the second secondary finders of all the positions in one group are used before any of the third secondary finders, the arrangement may be such that the second and third secondary finders of one position are used before the second and third secondary finders of the next position, and so on. If a first secondary finder becomes free while the switch WS<1> is in its second or third position, or if a second secondary finder becomes free when the switch WS<1> is in its third position, circuits are closed over a lead N1, whereby the relay PR is energized and closes the circuit of a motor magnet DR, which turns the switch S in the opposite direction to the magnet DV, so that the arm 15 or 26 of the switch WS<1> becomes operative, and the next call is set up over the finder that has become free. Similar arrangements can be employed with continuously rotating call-finders which are stopped when they reach the contacts of a calling-station. In this case, the circuit arrangements are adapted not to discriminate in the starting but only in the testing of the callfinders, while the current necessary for energizing the test relays is led over a selector similar to the distributing-switches WS, WS'.