Patent GB-302140-A (GB)
Title: Circuit arrangement for telephone installations with semi-automatic working
IPC: H04Q3/58
Filed: 1928-03-16
Abstract: 302,140. Siemens & Halske Akt.- Ges. Dec. 10, 1927, [Convention date]. Semi - automatic exchange systems.- In a system comprising a number of small automatic exchanges A, B, C, Fig. 1, some of which are connected in series to a central exchange D at which the establishment of all calls in the system is controlled, only a single inter - exchange junction is used between exchanges such as A and B and the arrangement is such that when a connection has been established, the junctions not in the direct talking route are released. Thus during a conversation between subscribers N1 N4, the junction A-D is released, whilst during a conversation between subsubscribers N3, N4 in the same exchange all junctions are free. Each of the exchanges A, B, C contains similar apparatus comprising a finder-connector link AS-LW, and a hunting switch AW which associates the links with the inter-exchange junction. In the intermediate exchange A, the junction A-B is connected to the finder and connector banks in the same way as a subscriber's line. Call between subscribers N1, N2; non-numerical connection to central exchange. The calling subscriber's magneto operates winding I of relay T, Fig. 2, which partially operates to close a locking circuit ineluding relay Au to connect winding III to the test terminal. Relay Au starts the finder ASI and when the calling line is reached, test relay P operates in series with winding III of relay T which now pulls up fully. Relay C, Fig. 3, also operates in the test circuit, locks up, and energizes the starting relay R1 of the switch AW1. When the link AS1- LW1 is found, relay I energizes in series with test relay P2. A momentary earth from contacts 18g, 16g is thus placed on junction lead a2 causing the operation of relay A and lamp AL at the operator's position, Fig. 4. Relay I also energizes relay V1 which operates relay G, the latter locking and releasing VI. Control of connector LW1 by central operator. When the operator plugs in, and throws key ATa1, relay K operates over lead a2 and coil Dr3. Having learnt the required number the operator transmits impulses at springs 59in, each impulse causing relay J, Fig. 3, to operate over lead b2, thus repeating the impulse to magnet Dm3. At the end of the impulses, the relapse of relay V1 connects up the test relay P3 and if the wanted line is idle, relay P3 switches through, and the operator rings by means of key RM. When the called subscriber replies, the operator withdraws the plug, disconnecting relay K which short-circuits relay P2 so that the junction a2, b2 is released. Relay H which was energized by relay K remains locked over contacts 61p3 32e, 24c. Release. A clearing signal is given by the operation of a subscriber's magneto, energizing relay S which completes a circuit for winding I of relay V2. The latter unlocks relays T, P, C, P3, H, G, S, and completes a circuit over contacts 66h, 93z for magnet Dm3. The holding circuit for relay V2 over its winding III and connector wiper 85 is opened at contact 69dm3 causing relay V2 to release followed by magnet Dm3. Relay V2 then operates again and the interaction continues until wiper 85 passes off bank 86 when the normal position is reached. Busy release. When the operator takes down the plug after receiving the busy signal, relay K releases, relay V2 operates over its winding I and contacts 65p3, 87h, 67k, 93z, and release occurs as before. Call between subscribers N1, N6. The calling line N1 is connected to the operator as before who, on hearing the wanted number, inserts plug ASt2 in the jack of the junction leading to the exchange C. In the switch AW3 (similar to the switch AW1, Fig. 3,) relay X operates over the a-wire and coil Dr2 and causes the switch to hunt for an idle link. When one is seized, relay P2 energizes in series with a relay E in the connector LW3 (which is identical with that shown in Fig. 3). The operator then throws the key ATa2, operating relay K, and establishes the connection as before, both trunks A-D and C-D being used for conversation. Clearing s gnals are given by magneto currents which operate relays S1 S2, to light lamps SL1, SL2. Call between subscribers N1, N4. The call proceeds as described above for a call to subscriber N2 and the connector LW1 is set to the contacts of the junction leading to exchange B. In this position wiper 85 engages contact 96 so that on the relapse of relays V1, relay U operates and connects relay Z to the test wiper, and if the junction is idle relay Z operates. Relay U switches through and a further digit is repeated by relay J at contact 88i to set the connector LW2 (similar to LW1). When plug ASt1 is withdrawn, junction A-D is released as before but junction A-B is held since relay K in connector LW2 is maintained operated over coil Dr and contacts 89u in LW1. Call between subscribers N3, N4. The calling line is connected non-numerically over switches AS2, AW2, AS1, AW1 to the operator who sets connectors LW1, LW2 as in the preceding paragraph. In this case, however, relay Z in connector LW1 does not operate since it is shortcircuited over relays P,C. When therefore relay K at connector LW1 falls back and releases junction A-D, relay V2 operates over contacts 65p3, 87h, 67k, 93z, releasing connector LW1. Relay K in connector LW2 then falls back and releases junction A-B.