Patent GB-615505-A (GB)
Title: Improvements in or relating to telephone systems
IPC: H04Q5/00
Filed: 1945-12-15
Abstract: 615,505. Automatic exchange systems. TENCH, F. (Automatique Electrique Soc. Anon.). Dec. 15, 1945, Nos. 452/48 (divided out of 615,448) and 32570/46. [Class 40 (iv)] Party lines, particularly those of the type described in Specification 615,504, are divided into sections in such a manner as to enable all sections to be used simultaneously either on inter-section calls or on calls between stations in the same section. Terminating circuits are provided at the two exchanges and connecting circuits between each two sections. Specification 615,448 also is referred to. In the system described, a party line extending between two automatic exchanges and divided into three sections comprises two terminating circuits (Fig. 3), two connecting circuits (Fig. 2) and the requisite number of substations (Fig. 1). When a subscriber removes his hand-set 8A, PI and IRS pull up and a seizing pulse is transmitted as a positive pulse followed by a negative pulse to which the P relays of all other stations respond, the HA and 41 relays following. At the calling station the pulse is terminated by ICI, and PI falls away. The latter relay is re-operated when the dial is moved off-normal and the impulses sent to line by IRS operate the P relays and stop the uniselectors at all other stations. At each station Z is cross-connected to the contact in bank 2 corresponding to the first digit of the station's two digit number, while X and V are crossconnected to contacts corresponding to the second digit. As the same first digit is used for all stations in the same section, relay I will hold at all stations in the wanted section, the reception of the second digit then extending earth over UN2 at the wanted station only, to ring the bell, ring back tone being transmitted over relay P. On the reply of the called party, operation of his A relay over UNI and X releases 3HA and the selector is homed, whereupon PI comes up to transmit the reply pulse during the operate time of ICI which disconnects the bell. Release is initiated by the subscribers, the relapse of A bringing up PI momentarily, and IRS transmitting, during the release time of the latter, a single positive pulse which releases the HA relays at the other stations in the section. The operation of a priority push-button PR enables a subscriber to break in on an existing connection, by bringing up ICI. General calls. A call may be set up to all stations in a section by dialling the section digit followed by O, the relevant contacts of UNI and UN2 being strapped to Y and U so that all stations are rung over UN2. For a call to all stations on the line 21 is dialled, permanent connections being provided in the selector banks at all stations. Connecting circuit (Fig. 2). A seizing pulse from the left-hand section brings up PG, followed by HG, ID, 51 and IRS, and the pulse is repeated to the right-hand section. Incoming digits are repeated by IRS to the right-hand section and to the switch 3UN. Discrimination on the first digit is effected by strapping XC to the bank contacts of 3UNI corresponding to the first digit of sections to the right and of the exchange terminating the right-hand end of the line and by similarly strapping XD to 3UN2 for the left-hand sections and exchange. When 51 releases at the end of the first digit, and the call is not for the right, no circuit exists for 6I, so that ID falls away, but DS comes up, homes the selector and re-operates ID to initiate the transmission of the release pulse. If the call is for the right, or if discrimination is not possible on the first digit, the release of 5I is followed by that of ID, whereupon 6I pulls up, re-operates ID and closes a second impulsing circuit for the magnet. If the call is for the right, the release of 6I at the end, of the second digit will bring up 3CNA, over 3UN5 and a strapping to Z, thus preventing operation of DS. Relay PD responds to the called party answer signal which is repeated by IRS to the left-hand section, during the operate time of IHD. Relays PD and PG fall away to the release pulses and initiate the restoration of the circuit to normal. Busy conditions; generation of busy tone. If the right-hand section is busy when a call is initiated from the left-hand section HG and HD are up and 3CNA cannot operate, but 1BB comes up in its stead, disconnects DS and stops the uni-selector, while at 3UN6 in conjunction with IBT it generates and transmits busy tone until the calling party hangs up, whereupon the release pulse releases PG, HG and IBB, DS coming up to home the uni-selector. Terminating circuit (Fig. 3); calls from party line subscribers. A seizing pulse is transmitted to the terminating circuit bringing up 4P followed by 3S, HE and AE, and the dialled digits are repeated by 3S to the switch 2UN. If the call is for a party line subscriber and the section adjacent the terminating circuit is not involved, a release pulse from the connecting circuit at the far end of the section restores 4P, and 2UN homes restoring the terminating circuit to normal. If the call is for the section adjacent the termination, S and HE hold up and the line is marked busy in the selector banks. The contact of bank 2UNI corresponding to the first digit of the exchanges is strapped to X so that when AE falls awayafter the reception of that digit IBE pulls up to render the second digit effective. If the call is for the other exchange, the release of IBE at the end of the second digit is without effect and the equipment will be released by a release pulse as above. If the second digit is that of the exchange shown, DE pulls up over 2UNI and a strapping to Y, and extends an impulsing loop to the preselector, over which 3S repeats the dialled digits. On the reply of the called party, ID pulls up, 2RS coming up to send a reply pulse, while the relapse of ID at the end of the call again brings up 2RS to send the release pulse. Incoming calls to the party line. On seizure from the exchange 9A operates followed by 4HA, 4HB to busy the line and send a seizing pulse. The dialled digits are repeated by 9A to 2RS and thence to the line. Operation of 4P to the reply pulse brings up 3S and IBR to reverse the battery connections to the incoming leads. Release is under the control of the calling party.