Patent GB-194464-A (GB)
Abstract: 194,464. Pollak, J. E., (Siemens & Halske Akt.-Ges.). Jan. 12, 1922. Semi-automatic exchange systems.-Relates to systems of the kind described in Specification 194,646, in which the depression of a key, or the insertion of a plug in a jack, corresponding to the desired exchange, connects up an impulse-sender and determines the transmission of the required number of impulses to select a line leading to the desired exchange. According to the present invention, the impulse-sender generates either a single series or a plurality of series of impulses according to whether the call is to be extended direct to the wanted position or exchange or indirectly through a third exchange. The impulsesender is adapted to repeat the impulses initially generated to set up the call over another route if the route first tested has no free lines available. If there is no free line leading to the desired exchange in the level of the group selector first chosen, the wipers are raised one or more additional steps to a level having access to a third exchange and the second (repeated) set of impulses operates a group selector at that exchange to extend the call to the desired exchange. As described in Specification 194,646, the jacks I - - VI are connected to a position selector PW which connects up the impulse-sender JW shown in the lower part of Fig. 2. The terminals, corresponding to multipled jacks, engaged by the wiper 56, are connected in inverse order to sections I, II of the sender and control the repetition of a set of impulses when required, while those engaged by wiper 109 are connected to sections III, IV and control the transmission of two distinct sets of impulses. Extension of call to idle group selector GW1. The insertion of a plug VStp in a jack corresponding to the wanted exchange causes relay R to energize the rotary magnet D<1> of pre-selector IVW which rotates until the test relay T1 energizes in series with relays R2, R1. Relay R1 energizes magnet D2 of pre-selector IIVW, which rotates until it finds an idle group selector, when the test relay T3 energizes over 20, 24, Tl (II), R2, R1(I), T3, 28, 30, C1, and locks up over contact 31, disconnecting winding R1(II). Relay C1 moves the control switch into its second position, in which the b-lead is earthed over 36, 44, 39, and auxiliary test wiper 38. Operation of position selector PW. The relay R also energizes a starting relay An which causes magnet D to rotate the selector PW until it finds the trunk IVW, when the test relay P is energized over wiper 12 and earths the wipers 56, 109. Operation of impulse-sender. Assuming that the plug VStp has been inserted in jack I, the wiper 56 engages contact 57, thereby grounding contacts 58, 104 in the path of arm 55. As soon as an idle group selector has been found, the relay F energizes over the circuit 43, F, 16, 41, T2(I), and the b-lead, and closes a circuit 45, 46 for relay U and motor magnet D4, which moves the arms 43, 48, 55, 60 one step. The magnet D4 is then intermittingly energized over a circuit 46, 50, 49, 48, 54 and steps round the sender until the arm 55 engages the contact 58 grounded by wiper 56, whereupon relay P3 energizes, locks up, and prepares the circuit of relay J. At, each following energization of magnet D4, relay J is energized and sends an impulse over the a-lead to the relay A1 of the group selector. When the arm 60 leaves segment 61 relay P3 de-energizes and' disconnects relay J. The arm 60 then energizes a pair of slow relays K,S1, which control magnet D4 in such a way that the sender moves slowly over the next three steps so as to give time for the rotary movement of the group selector. If the selector is able to make the connection over the selected level, the impulse-sender completes its rotation without sending further impulses. If, however, all the trunks in the selected level are in use, the b-lead is again earthed at the selector, and the relay W, Fig. 2, energized over the b-lead. 34, T2(I), 41, 16, W(I), 88, 43, as the arm 43 passes over contact 88. The relay W locks up over its winding II and segment 103, and prepares a circuit for the relay P3 which, when the arm 55 reaches contact 104 is energized over a circuit 15, 56, 104, 55, P3(I), 105, 103, 43. Relay P3 locks up over contacts 62, 106, 107 and connects up relay J so that at each following energization of magnet D<4> an impulse is sent over the a-lead as before to raise the selector of the second exchange to the same level as that to which the selector at the first exchange was initially raised. If the plug VStp is inserted in a jack VI, say, corresponding to an exchange which must be reached through an intermediate exchange, the corresponding contacts 125, 124 engaged by wipers 56, 109 are connected to contacts 111, 126, 127 in sections I, III, IV of the sender, no provision being made in this case for the repetition of the first set of impulses. In this case sets of three, six, and one impulses are sent to operate selectors at the first, intermediate, and final exchanges. Group selector. The relay A1 repeats the selecting-impulses to the lifting-magnet HI through a relay V4 which, by de-energizing relay V5, at the end of the impulses normally moves the control switch into its third position, in which the switch rotates to find an idle trunk. If, however, all the trunks in the selected level are in use, the terminal 73, say, engaged by the auxiliary wiper 38 is earthed by the relay G1 controlled by chain relays such as CG1, and the relay B sends an extra impulse to the lifting- magnet. This is repeated if all the trunks in the next level also are busy. The clearing signals and release are controlled as described in Specification 194,646.