Patent GB-197666-A (GB)
Abstract: 197,666. Siemens & Halske Akt.- Ges. May 15, 1922, [Convention date]. Automatic exchange systems; metering.-Calls set up by district-office subscribers are metered differentially, according as the wanted subscriber is located in the district office, in the main exchange, or in another distant exchange, under the control of auxiliary switches associated with the outgoing ends of trunks to the main exchange which respond to the first one or two digits of the wanted number. Local calls are charged one unit only, irrespective of the duration of the conversation, but calls to main or other exchanges are charged also according to duration, the auxiliary switch operating in response to the first digit to select one of a series of interrupters which transmit sets of one, two, three &c. impulses at regular intervals throughout the connection to control, the further operation of the calling subscriber's meter. In the system described, local calls are established normally over local apparatus without tying up main-exchange trunks, but, if all the local lines are busy, the connections are set up over trunks to and from the main exchanges, the metering of a local call being the same, irrespective of the route over which it has been established. A calling subscriber Tn1, Fig. 2, is connected over first and second preliminary selectors IVW1, IIVW1, to a repeater set Ue, associated with the outgoing end of a trunk VL1, Fig. 3, leading to the main exchange. An auxiliary switch MS responds to the first one or two digits of the wanted number, which are also repeated over the trunk VL1, and if the first two digits are 34 denoting a local connection and a local line is available, the trunk VL1 is released and the second preselector IIVW1 is restarted to hunt for an idle local connector LW1 over which the connection is completed. The switch MS also effects the differential control of the metering, over a second wiper 69, and, in the case of calls to the main or other exchange, sets of impulses are periodically transmitted over wiper 69 to a step-by-step switch ZS1 which stores up the impulses until the end of the conversation, whereupon a second switch ZS2 operates under the control of switch ZS1 to transfer the accumulated charge to the calling-subscriber's meter Z. In a modification, Fig. 4, the metering of all calls, whilst dependent on the location of the wanted subscriber, is independent of the duration of conversation. First and second preliminary selectors, IVW1, IIVW1. When the calling subscriber removes his receiver, the line relay R1 closes contact 1 to energize the stepping magnet D, which rotates the wipers until a free line is reached, when test relay T1 energizes in series with relay R2 to stop the wipers, and to short-circuit its winding I to mark the selected line busy. Relay R2 starts up the pre-selector IIVW1, and when an idle repeater Ue and trunk VL1 is reached, the test relay T2 energizes over the circuit 15, 17, 18, 19, C1 to stop the switch, to connect the substation Tn1 to relays A1, B1 which energize, and to extend the holding circuit for pre-selector IVW1 over contact 115 and winding II of relay T2 to wiper 15 and the repeater Ue. Repeater Ue ; local call completed over local connector. Relay C1, energizing in series with relay T2, completes a circuit over contact 22, winding II of relay Cl, contact 24 (which shortcircuits relay V2), and winding I of slow-release relay VI which energizes. Magnet D2, energized over contacts 31, 30, 29, 128 advances the wipers 30, 69 one step. The three impulses of the first digit are repeated by relay A1 over contacts 33, 32 and conductor 34 to the main exchange and over contacts 128, 42, 43 to magnet D2 which steps wiper 30 on to terminal 44. At each impulse, the opening of contact 24 removes the short-circuit from relay V2 which energizes to complete a circuit over contacts 36, 38, 39, 28 in series with both windings of differential relay B2 which does not energize. Upon the relapse of relay V2 at the end of the digit, relays U1, E are energized in parallel over contacts 128, 29, 44, 46, and, if an idle local line is available as indicated by the non-energization of a relay G, relay U1 1 locks up over contact 48. The second set of four impulses moves wiper 30 to terminal 50, and, upon the release of relay V2, a circuit 128, 29, 50, S, 49, 54, U, is completed, in which relay U energizes to restart the pre-selector IIVW1, the wipers of which rotate under the control of the test relay T2 (now connected to a second test wiper 57) until an idle connector LW1 is reached, when relay T2 responds and the connection is completed in known manner. The meter Z is operated by an increase in current transmitted from the connector over the conductor 58. Wiper 69 of switch MS is in contact with terminal 74, but the energization of relay E prevents the transmission of any further metering impulses. Relay S energizes in series with relay U to open contact 18, and upon the de-energization of slow-release relays C1, VI, relay V2 energizes over contacts 61, 62 in series with winding II of relay S, thereby completing a circuit 65, 63, 42, 43, 31 for magnet D2 which advances the wipers 30, 69 one step. The closure of contact 66 short-circuits relay V2 which de-energizes and in turn breaks the circuit of magnet D2. The wipers are thus stepped forward under the joint control of relay V2 and magnet D2 until the normal position is reached, when the opening of contact 62 terminates the movement. Local call completed over main exchange apparatus. If all the local lines are busy, contact 48 is open, so that relay U1 falls back as soon as wiper 30 leaves contact 44, and at the end of the second digit, the circuit 128. 29, 50. S, 91, F is completed in which relay F alone is energized. When the called subscriber replies, the closure of a contact 103 energizes relay B2. When the calling subscriber hangs up, the relapse of relay C1 completes a circuit 72, A2, 34, 75, V1 in which relay A2 operates to energize metering relay ZR over the circuit 83, 82, 35, 38, 77 in series with relay U2. Relay ZR, by closing contact 84, increases the current over the test lead 17 to operate the meter Z. Relay A2 also energizes magnet D4 to step wiper 40 on to circuit 79, thus shortcircuiting relay B2 which releases. Relav U2 short-circuits relay A2, relays V1, C2 release, magnet D4 and relay U2 are alternately energized over circuits 90, 88, 89 and 76, 27, 80 respectively to step wiper 40 back to normal. Call to distant exchange, characterised by a first digit 5. In response to five impulses, wiper 30 engages contact 93 and, upon the release of relay V2, relay F energizes over contacts 93, 29, 128 to prevent any further operation of the switch MS by subsequent digits and to prepare a circuit from wiper 69 to magnet D3 which is completed by relay B2 when the called subscriber replies. Three impulses per unit of time are then transmitted throughout the conversation over contacts 105, 96, 69, and magnets D3 to storing- switch ZS1, the wiper 86 of which is moved into engagement with contact 97 (say) When the called subscriber hangs up, wiper 40 is moved forward one step and one impulse is transmitted to relay ZR as described in the previous paragraph. When wiper 40 reaches contact 79, relay B2 is not short-circuited, relays A2, U2 energize again and transmit a further impulse and the wiper 40 is moved on step by step, one metering impulse being transmitted for each step until contact 100 is reached when relay B2 is shortcircuited over contacts 97, 86, relays VI, C2 release and switches ZS1, ZS2 are stepped forward to normal under the control of relay U2. Modification, Fig. 4, in which charge is independent of time. The terminal bank of the wiper 69 of the switch MS is directly associated with the switch ZS2, Fig. 3, as shown; and in response to the setting of wiper 69 on contact 96, the wiper 40 is stepped forward in the same manner as described above until the fourth contact 101 is reached, thus effecting the transmission of three additional metering impulses.