Patent GB-479852-A (GB)
Title: Improvements in or relating to automatic or semi-automatic telephone systems
Filed: 1936-08-11
Abstract: 479,852. Automatic exchange systems. AUTOMATIC ELECTRIC CO., Ltd., (in Liquidation), GILLINGS, C., TAYLOR, R., and BAKER, G. T. Aug. 11, 1936, No. 22120. [Class 40 (iv)] A bidirectional selector which is adapted to hunt over groups comprising a main part in one level and additional lines in the same and/or other levels is controlled by a marking switch which may be individual or common and which is itself set by marking from the selector. After searching in a level, the selector restores and is reset by marking to the next level in which search is necessary. In a P.B.X. final selector having two sets of wipers chosen by the route of access, the additional lines of a group are marked by the auxiliary switch after the main part has been searched and may be reached over either set of wipers, double hunting taking place when necessary. In a two-digit group selector, the auxiliary switch marks the lines of a group in each level in which they appear and double hunting takes place. Provision is made in the latter arrangement for a predetermined number of re-searches at timed intervals. The selectors are of the rectangular release type described in Specification 391,151. P.B.X. final selector, Figs. 1, 2 (Prov.). The vertical and rotary magnets VM, RM respond to the incoming digits in the usual manner under the control of dialling relay C and change-over relay E. Discrimination in accordance with the route of access (odd or even hundreds digit) is effected after the first rotary step by relay WS. In the interval between the relapse of C and E, the test circuit is made over PA or PB (upper) and HA or HB to wiper P1 or P2. Assume first that the selector is not wired for divided groups ; in this case the switch DM is not used and the sets of terminals K, L, M and G, J, E re connected together. The first lines of P.B.X. groups in banks M1, M2 are wired to terminal A and the intermediate lines to teterminal B. If the first line of a group is busy therefore, the test circuit is ineffective, but PA (lower) energizes over wiper M1 (assuming for simplicity that WS is back) and connects up HT, HS. The latter holds and initiates hunting, the rotary magnet BM interacting with HT and PA. If an idle line is found, PA (upper) holds in series with HA (C is up again at this time) and the disconnection of PA (lower) is without effect. Relays HT, HS fall back and the connection is completed in the usual manner. If the last line is found busy, there is no circuit for PA, so that HT, HS fall back and the rotary magnet RM self-steps to position 11, in which PA (lower) energizes over J, E and locks (upper in series with HA. A busy signal is sent over 11th step springs S. If any group is extended to include spare outlets at the end of the same or other levels, the switch DM is used. Hunting over the main group takes place as described above, and if all the lines thereof are busy, on the relapse of HS, the switch DM steps to a position marked over M1, Q, 3d. Additional lines at the end of the same level are now marked in banks M1, M2 over P, 4d. Relay PA operates momentarily to connect up RK, HS, and the rotary magnet RM self-steps to the first of the marked lines, whereupon PA or PB or both pull up, and the search continues over these lines, which may be reached over either set of wipers since RK is up. The rotary magnet RM continues from the last marked line to position 12, from which the wipers return to normal. Relay HS falls back and the vertical magnet VM self-steps to the level marked over VW, R, 2d. Relay PA operates momentarily, connecting up HT, HS, the switch DM moves one step to mark further lines and the rotary magnet RM advances thereto by self-stepping. If these all test busy, in position 11, PB (upper) energizes over G, 3d and locks (lower) over HB, and a busy signal is sent. If an individual line is busy on the relapse of E, the switch DM moves to its end position in which PA operates momentarily over 3d to connect up HT, RK, HS, whereupon the rotary magnet RM moves to position 11, PB energizes over C, 4d and a busy signal sent. The switch DM restores upon release. Two-digit group selector, Figs. 1, 2 (Comp.). Change-over relay E locks independently of dialling relay C, and on the relapse of the latter after the second incoming digit, the switch OM moves to a position marked over M, B, GM3 in which PA energizes and connects up SK, which disconnects E. Meanwhile the first pair of lines are tested and HX, HY are inoperative if both are busy, and the relapse of E closes a self-stepping circuit for the rotary magnet RM, the test circuits for subsequent pairs of lines of the group being completed over SW, A, GM4. If there is no idle line in the level, the drive continues to position 12, from which the wipers restore to normal. Relay C energizes again and the vertical magnet VM steps to the level marked over VW, C, GM2, whereupon PA energizes, releases C and advances GM one step to mark the appropriate lines in the fresh level over which hunting takes place as before. If the whole group has been searched without result, the selector is reset to the original level by marking over GM2 and on the advance of GM, relay RS energizes over E, GM2, while the first lines of the main group are marked over M, B, GM4. The rotary magnet RM steps to the marked position and PA pulls up and shortcircuits SK. No test takes place at this stage. Relay E reoperates and the switch GM goes to normal and then after an interval determined by relay TP, which is connected to a time pulse lead, to the position originally marked over M, B, GM3. The first pair of lines are now tested and the whole search is repeated. Each passage of the switch GM through normal advances a switch SP one step and after a predetermined number of searches, RN energizes and applies a busy signal. When an idle line is found, HX or HY operates and connects up switching relay HA or HB, and homing circuits are made for the switches GM, SP. If the selector is set numerically on lines of a group other than the first, the switch GM moves to its end position in which PA energizes followed by SK, RN and a busy signal is sent if both lines are busy. Upon release rotation is resumed until position 12 is reached, and the wipers restore to normal.