Patent GB-495582-A (GB)
Title: Improvements relating to circuit arrangements for automatic selecting switches in telephone systems
IPC: H04Q3/42
Filed: 1937-07-09
Abstract: 495,582. Automatic exchange systems. SIEMENS BROS. & CO., Ltd., LONG, D. P., and PETERS, C. L. July 9, 1937, No. 19072. [Class 40 (iv)] In a system in which a twomotion switch hunts in a level marked in accordance with the operation of code-responsive relays, operation or re-operation of one or more code relays takes place after an unsuccessful search over this level to provide a marking for a further search. Three arrangements are described. In the first, the switch is set in accordance with two digits and hunts initially over a single level if set to the first line of a group. If all the lines are busy the call is extended to a storage circuit and the code relays are given a new setting. Subsequently the switch is restored and re-operated in accordance with this setting. In the second arrangement, the searches may take place over several levels in succession. In the third arrangement the switch has two sets of wipers and takes only one digit and a group may occupy several levels but if the whole group is busy, the switch is released, no storage circuit being employed in this case. First arrangement, Fig. 1. The switch is seized by grounding the wire P to energize TC. The code sender then puts battery on one or more of the wires -, +, N-, N+ to operate one or more of the code relays W .. Z, and these mark a particular terminal in the vertical bank VB, by connecting relay VT to it, and complete a self-interrupting circuit for the vertical magnet V which is interrupted by VT when the marked level is reached. VT also locks and energizes VR which locks. Owing to the change-over of off-normal springs N3, TC falls back sluggishly when the switch stops and releases the code relays and VT and the latter makes a circuit in which TC is re-operated. The code relays are then re-operated in accordance with the next digit and the rotary magnet R drives the switch to the position marked in bank M2 under control of VT. TC then falls sluggishly but before its relapse a circuit is made over wiper M1 and one of the wires OL which are connected to terminals corresponding to the first lines of groups. A, or B, or both A and B are energized, according as the selected group is the first, second or third in the level. A shunt is removed from G which is then operated in the same circuit, locks up over G(ii) until the circuit is released, holds the relays A, B and grounds the wire OOL of the selected group. The wires OOL are connected to the M1 terminals of the respective groups other than the first. A test circuit is made also over T(i) and (ii) and if the outlet is idle T marks it busy and allows H to pull up. T is then shunted out but H maintains the busy mark and switches through. On the relapse of TC, VT and the code relays are released. If the outlet is busy, T and H are not operated, and the relapse of UT makes a self-interrupting circuit for the driving magnet. T operates when an idle line is found and stops the switch. The lines in the group need not be contiguous since only those marked over OOL in bank M1 are tested. If all the lines are busy, the switch is stopped on a storage circuit. The P terminals of the storage circuits are connected to AS which pulls up and energizes either, neither or both of the code relays Y, Z over their windings (ii), and post springs NP1, NP2, and, except on levels 9 and 0, energizes one or other of the relays W, X over the vertical wiper and these code relays lock up. A characteristic tone signal is given to the operator and ground applied at her position to the -wire energizes TC to remove the tone. When she receives a signal that a trunk is available she grounds the wire SU to operate RS(ii) which locks over RS(i) and releases H, AS. TC then falls. The switch wipers are driven to the end of the bank when H falls and then drop and are restored to normal. Relays VR, RS are released. The switch is then reset vertically in accordance with the condition of the code relays. VT operates when the marked level is reached, stops the switch, energizes VR, releases the code relays and then falls itself. The switch then advances over the level, testing the trunks marked over the wire OL as previously described. Single trunks are tested in the same way as first lines. If such a trunk is busy, the relapse of TC energizes PG which locks and connects up busy tone. When the line becomes idle, PG is unlocked and TC operates. Flicker earth is connected to the supervisory wire SU and the operator then energizes RS. VT is thus operated and then relays T and H as when a line is idle when first tested. TC, RS, VT are then released. The circuit is released by removing ground from the private wire to release VR, and, if necessary, G. H is then released and the switch is driven to the end of its bank and restored. Second arrangement, Fig. 2. As before, the switch hunts vertically for a terminal marked in the bank VB1 by the code relays W .. Z under control of VT. VR operates at the end of this movement, locks up and releases TC. VT and the code relays are then released, TC pulls up again, a new code signal is received and the switch advances to the terminal marked in the bank M2. If the line is the first of a group, X, Y, Z are all operated and the operation of VT to stop the switch therefore energizes G. If this line is idle it is seized by relay T and H pulls up releasing T as in the switch shown in Fig. 1. If it is busy the switch hunts over the level on the relapse of TC and the code relays, all the terminals in the M1 bank associated with groups being connected to ground. If the level is busy and there are more trunks in the group on other levels, a circuit is made over 11th step springs and vertical wiper VB2 for the code relay W or X, and the relays Y, Z are operated as necessary over the last terminals in the level of the P and M2 banks. RS is operated over 11th step springs and the last N-terminal and shunts 11th step springs S2 to re-start the rotary magnet. The switch is then restored and NRS, VR fall back. The switch then hunts vertically for the new level marked in the bank VB1 and hunts in the selected level as previously described. If this level is busy and there are further trunks in the group the switch is similarly set to a third level. If the whole group is busy wiper P reaches a contact connected to battery over rs4, in an 11th step position in which access is given to a storage circuit. Relays T and H operate as when a trunk is seized and a tone signal goes back from the storage circuit. The operator then energizes TC(ii) over an 11th step contact S5. TC locks and cuts off the tone. The code relays relevant to the first level of the group are operated over VB2, M2 and P. When the operator learns of a free trunk in the group, she energizes RS over SU. H is released and the switch is restored and hunts as before. If the line called is an individual one, X, Y, and Z are not operated together, and G is thus not energized when rotary stepping begins. The outlet is seized as before, if idle, but if it is busy the relapse of TC energizes PG(i). PG locks over PG(ii), VT and the code relays fall back and busy tone goes back over contacts of PG. When the line becomes idle, the relapse of PG re-operates TC, and the operator is given a flicker signal and operates RS. This energizes VT and T is then able to seize the line as before. Third arrangement, Fig. 3. K is operated over the private wire to seize the switch and the code relays W .. Z are operated and mark a level in the vertical bank VB. HA, which subsequently acts as a switching relay, is energized over HA(i) in parallel with the vertical magnet which steps the wipers to the marked level and is there stopped by one of the normal test relays TA. On the relapse of HA, TA is released to complete the rotary driving circuit. If a free line is found by wiper P1, TA operates and stops the switch and HA, HC pull up in series, to switch through and disconnect the code relays, and lock themselves up. TA is then shunted out. Similarly if P2 finds an outlet, TB, HB, HC are operated. If the group called is one occupying only one level, Z is operated and if the level is busy, TB operates over last contacts energizing HB, HC and busy tone and flash signals are given to the operator. If however the group comprises a further level, Z is not operated and TA is operated over PI and operates Z over 11th step springs. Z locks and TA is then released to re-make the rotary driving circuit. The switch is then restored, hunts vertically for a position marked by relay Z and the other code relays (which are still operated) and then hunts over the new level as previously described. If this level also is busy, a busy signal is given as in the case of single-level groups. If a spare level is picked up the operation is similar but the operator receives a characteristic tone signal. An overflow meter OFM is operated when a whole group is busy.