Patent GB-256295-A (GB)
Title: Improvements in or relating to telephone systems
IPC: H04Q3/42
Filed: 1925-04-01
Abstract: 256,295. Standard Telephones & Cables, Ltd., (formely Western Electric Co., Ltd.), Searle, A. M., and Baker, J. H. E. April 1, 1925. Automatic exchange systems.-In a code-translating register-controller the sender control switch is moved off-normal in a circuit over one of its own wipers if the impulse springs are working correctly. If it remains in its normal position, a circuit is made by the digit distributor switch in its third position for giving an alarm, releasing the register controller and marking it permanently busy. Means are provided to prevent the transmission of impulses while the sender control switch is moving from the position corresponding to the last office digit to that corresponding to the first subscriber-digit. Transmission is held up by the reversal of current in the loop when a switch is not ready to receive impulses, but this feature is described after the office, digits have been sent to prevent abnormal operation if a called party answers before the register controller has been freed. Specification 150,300 is referred to. Selecting and setting A-digit switch. When the subscriber is extended to the first code selector, Fig. 1, line and release relays B1, D1, and impulse relay A1 pull up and start the hunting switch, Fig. 2, in a circuit D1-5, P, D1-8, ROT. When an idle switch is found, relay K1 which is no longer short circuited connects relay A3, Fig. 3, in place of the upper winding of the line relay B1, substitutes the resistance R3 for the windings of relays F1, G1 in the circuit of relay A1 and takes release control from relay D1. Relay A3 repeats the A-digit to magnet VERT, and springs ON energize stepping relay E3 which, on the relapse of the series dialling relay C3, interacts with magnet ROT in the usual manner until an idle register controller is found. Relay D3 thereupon extends the impulsing circuits and locks up to ground sent back from the register controller and relays A3, B3 fall back. Automatic test of impulse springs. In the register controller, relays E4, F4 pull up, the impulse springs are started over IMS and a circuit over springs connected to LIS is made for relay Q4 which pulls up its armature 5 when the springs close and its remaining armature when they open. A circuit is thus made over inter. rupter springs connected to MIS for relay C4, which pulls up in a similar manner to relay Q4, and completes a self interrupting circuit for the magnet ROT of the sender control switch SCS which thereupon moves one step from normal releasing relay C4. If either spring, set is out of order, switch SCS remains in its normal position and when the digit distributor switch DD moves on after the C-digit is recorded, a circuit is made over DD2, SCS3 for relay H4 which energizes relays D4. R5 and grounds the incoming pulse wire to initiate release of the register apparatus as described later. Relay D4 and subsequently relay R5 keep the test wire grounded, lamp T is lit, and an alarm is operated over SFS. Registeration of remaining digits. Relay E4 repeats the B and C digits to the magnets V, RR of a Strowger-type register BCS and the numerical digits to the. magnets of simple registers MR, CR. DR, UR. Relay G5 pulls up at the beginning and relay J4 at the end of the first impulse of each digit and at the end of the digit these relays fall back in succession to deliver a timed impulse to the magnet ROT of switch DD. Transmission of office code. In its third position, wiper DD2 over SCS2 marks the first wiper of the register BCS and over SCS4 grounds one side of the springs MIS. Relay C4 pulls up in two steps, locks itself and connects the springs MIS to the magnet ROT of the sending switch SS which at its first step energizes pick-up relay A4 to remove a short circuit from springs LIS and to short-circuit relay L5. Impulses are thus sent out over +, -, until the sending switch finds the marked bus bar, whereupon stop relay B4 short-circuits the loop springs, removes the short circuit from L5, makes a homing circuit for the sending switch and energizes the magnet of switch SCS in a circuit B4-10, SCS4. When the sending switch reaches normal, relays A4, B4, fall back sluggishly in succession and switch SCS moves one step to initiate transmission of the next digit. Up to six digits may be sent in this way. Transmission of subscriber code. These digits are sent out in the same way as the office code but since the ground for starting the sending switch for any digit is derived from the off-normal arc of the register on which the next digit is recorded, the transmission of any digit is held up until the next is received. Release of register apparatus; statistical metering. When the final digit has been sent, the switch SCS grounds the wire DCO and relay D4 locks up, disconnects springs MIS, and causes the successive relapse of relays F4, Q4. Relay F4 energizes the release magnets PP, RS of the switch DD and the registers over the upper winding of the relay K4. In its normal position, switch DD completes homing circuits over the lower winding of relay K4 for the sending and sender control switches. Relay K4 thus keeps the test wire grounded while any switch is offnormal. In the instant between the relapse of relay F4 and the pulling up of relay K4 the test wire is grounded over E4-8. D4-6, N4 (BCS). When DCO is grounded, a metering relay is operated over MR. This does not take place in the case of forced release when the metering circuit is opened by relay H4. When the register controller is restored, relay K4 releases relays D3, to energize a release magnet RS, Fig. 3, and K1, Fig. 1, to re-connect the upper winding of relay B1 in the calling loop. First code selector. Relay A1 repeats the first code digit to magnet VERT and on the relapse of series relay C1, stepping relay E1 interacts in known manner with the magnet ROT. When an idle line is found, relay J1 extends the impulsing loop but keeps relay A1 locked up over its upper winding, grounds the test wiper and locks up. Completion and release of connection. When the called party replies, polarized relay F1 releases relay A1. When the calling party hangs up, relays B1, D1, F1 J1 fall back, release magnet PI is energized and a homing circuit is made for the non-numerical switch Fig. 2. Calls to " Enquiry " by dialling O. In its tenth level, the A-digit switch selects a special register controller designed to send an invariable code or preferably a register controller which appears also as a late choice in another level. In this level, however, the connections to the +. - terminals are reversed and when relay D3 switches through, the polarized relay L5 energizes relay P5 which opens the in-impulsing wire and connects the wipers of the register BCS to terminals on the frame CCF. As many of these as necessary are jumpered to the numerical bus bars and the next one to terminal CO. When relay P is energized, the transmission of impulses begins with the switch DD in its normal position and when the necessary digits have been sent the switch SCS grounds the wire DCO to release the register apparatus. Route code with fewer than six digits. Unnecessary terminals of the register BCS are jumpered to 19 and in the positions corresponding to these terminals the switch SCS completes a selfinterrupting circuit for itself'over the lower winding of relay K4. Relay K4 by disconnecting relay C4 makes it impossible for the sending switch to send a spurious digit during the movement of switch SCS. Delaying transmission. In case the apparatus ahead is not ready for a digit, current in the outgoing loop is reversed and relay L5 pulls up and completes a circuit SCS3, L5-5, B4-16, for relay B4 which keeps relay C4 disconnected to hang up the transmission. This circuit is broken when the sender control switch passes position 7 so that no effect is produced by current reversals during or after the transmission of the numerical digits, e.g. by the subscriber's answering while the register controller is still associated with the call. All register-controllers busy. If the A-digit switch reaches 11th terminals, springs CS change over, busy tone and flash is sent from BF and circuits are prepared for timed release of the switch as when the subscriber does not dial, (described below). Accidental impulses-A-digit. In response to a single impulse, the switch takes one vertical step post springs NP close, and the relapse of the series relay energizes the release magnet RS. Subscriber fails to dial the A-digit. TP is connected momentarily to ground every half minute. The first impulse after the energization of relay B3 causes relay F3 to pull up its armature 5 and at the end of the impulse the rest of its armatures, and if the switch has not been moved off-normal, the next impulse energizes relay E3 which grounds the wire PsW to shortcircuit relay Bl. Relay D1 falls back energizing relay H1 which re-energizes relay B1 over both its windings and the loop, lights lamp SL in series with a delayed alarm, and locks up. Relay A3 is held only until the time impulse goes off and then releases relay B3 which removes the busy mark to release relay K1. Impulse relay A1 is held in series with G1. If the subscriber dials at this stage, veitical magnet VERT, and series relay C1 are operated in a circuit D1-11, A1-6, Jl-25, relay A1 being de-energized at each relapse of relay Bl. Springs N change-over and energize relay J1 in series with relay E1 to connect up NU tone from NU. Subscriber fails to dial B, C or numerical digits. Relay M4 is connected on the energization of relay E4 to a time impulse TP and pulls up in two steps. At the next impulse, unless relay M4 has been unlocked by the operation of relay E4 by dialled impulses, relay H4 pulls up and by energizing relay D4 causes the register controller and A-digit switch to be released and if the subscriber dials he receives NU tone as when the delay occurs before t