Patent GB-421585-A (GB)
Title: Improvements in or relating to telephone systems
IPC: H04M7/06
Filed: 1933-06-21
Abstract: 421,585. Automatic exchange systems. AUTOMATIC ELECTRIC CO., Ltd., Strowger Works, Liverpool, and GILLINGS, C., 553, Sidcup Road, Eltham, London. June 21, 1933, No. 17728. Divided out of 414,106. [Class 40 (iv)] In an alternative routing system, the whole of the impulses required for setting up a connection, whether direct or indirect, are transmitted from the same impulse sender (dial switch or register controller) ; a group selector has access to direct and indirect junctions by a continuous hunting movement and if an indirect junction is selected, a signal is sent back so that additional digits may be transmitted to route the call through tandem. In non- register-controller systems, the signal informs the calling party that additional digits are required. In the register-controller systems described, the later outlets in levels of a bi-directional group selector give access to a common group of non- numerical switches which hunt for tandem junctions, the signal for additional digits being battery reversal at the non-numerical switches. The code-translating switch makes provision at a single setting for direct and tandem routing digits, but the control switch is stepped past the wipers controlling the transmission of tandem digits when a direct junction is found, In cases where this signal is already in existence for C.C.I. calls, modifications are made so that in such calls, alternative routing is effected in response to finding normal battery conditions. Alternatively, in C.C.I. calls, additional senders may be associated with the outgoing tandem junctions. Alternative routing in register-controller systems. The first code selector S1, Fig. 1, has direct junctions to tandem T appearing in level 2, direct junctions to nearby exchanges B and C appearing in the earlier positions in levels 4 and 7 respectively, while the later outlets in these levels give graded access to a group of hunting switches JH having access to the group of tandem junctions appearing in level 2. If S1 fails to find a direct junction to B or C, it seizes an idle switch JH which hunts for an idle junction to tandem T. The line wires to switches JH have reversed battery connections and this constitutes a signal to the registercontroller to transmit extra tandem routing digits, the normal battery connections being restored as shown in Fig. 2 when JH switches through. Figs. 3 to 5 show the modifications required in the register-controller described " Automatic Telephone Exchange Systems," Technical Instructions, XXV (part 6A) issued by the Post Office Engineering Department, these figures being modifications of Fig. 18 of the said instructions. If the first code selector finds an idle direct junction (normal battery connections) the D relay in the register-controller remains normal and when the control switch C, Figs. 3 and 4, steps on to wiper 2a of the BC switch, relay DCO operates, locks and connects contacts 3 to 6 of bank C2 of the control switch to the digit-cut-off terminal RCO so that C steps on and no further routing digits are transmitted. If there are no idle direct junctions, the reversed battery condition at the switch JH operates the D relay so that DR pulls up, locks and opens the circuit of DCO which therefore is not energized when C steps on, and the tandem routing digits are sent out. It will be seen that in both cases the control switch steps immediately from position 2 to 3. If this route does not require four digits, the unwanted contacts on the BC switch are jumpered to terminal RCO. If the tandem junctions appear in the second group selector, DCO is connected to wiper 3a of the BC switch instead of 2a. If a further exchange, say D, is normally reached through C but an alternative route exists through T, one or more banks 3a-5a: of the BC switch are connected to route the call from T to C and one or more of 4a-6a are connected to route the call from C to D any unused terminals being connected to RCO. The armatures of DCO must however be so arranged that the wipers of those banks required for routing the call from C to D over the more direct route, are not connected to RCO when DCO operates. In cases when the registercontroller already responds to battery reversal to delay sending the numerical digits in calls to C.C.I. positions, the arrangements in Fig. 5 are provided to discriminate between this condition and the alternative routing signal where alternative routes to C.C.I. positions are available. An additional terminal T1 and relay PZ are provided for connection to contacts of 2a corresponding to manual exchanges, and it is arranged that on alternatively routed calls to such exchanges, the D relay does not operate. The operations for a call to automatic are as previously described, but on a call to manual (reversed battery) DR, Fig. 3, pulls up and connects T1 to DCO so that this relay operates and the control switch steps on to the numerical position. If all the direct junctions are busy, switch S1, Fig. 1, becomes connected to a C.C.I. repeater and outgoing hunting switch which has normal battery connections so that DR, DCO are not operated and PZ pulls up, operates a relay (SZ) to hold up the sending while hunting is taking place, and causes the control switch to take a step. PZ and SZ then fall back slowly and the tandem digits are sent out. Alternatively, the alternative routing C.C.I. repeaters have reversed battery connections to hold up sending by the normal register-controller until an additional sender associated with the repeaters has inserted the tandem digits. The connection, on being switched through, has normal battery connections restored so that the register-controller proceeds to send the numerical digits. Specification 414,106 is referred to.