Patent GB-187207-A (GB)
Abstract: 187,207. Automatic Telephone Manufacturing Co., Ltd., (Assignees of Bellamy, J. I.). Oct. 12, 1921, [Convention date]. Automatic exchange systems; metering systems.-In a zone metering system, in which the charge for a call is determined solely by the distance between the originating and final exchanges, an assessing switch P, Fig. 3, associated with the outgoing trunk from the originating exchange responds to the first two digits transmitted over the trunk (i.e. to the second and third digits of the wanted number) so as to set itself in a position individual to the final exchange or subexchange and picks out one of a number of zone metering circuits 181 - - 192 connected to a common impulse switch I. When the called subscriber answers, the switch I at every alternate step from its starting position causes a booster impulse to be transmitted over the incoming test circuit to operate the meter, but on reaching the zone wire picked out by the switch P it disconnects the booster circuit. The switch P may be replaced by a single-co-ordinate switch 294. Fig. 5, which responds to the two digits in turn and controls a group of relays 256 - - 260, the effect of the later digit being varied according to which relay is energized by the earlier digit. A time switch T may be employed to transmit additional booster impulses to the meter, as long as conversation continues, with a frequency proportional to the charge initially assessed. The invention is designed for an area having an eventual capacity of 1,000,000 subscribers, and comprising 10 districts each having 10 exchanges of 10,000. Fig. 1, shows an originating exchange O with trunks leading to a largely developed 4th district, centering on the exchange 44, and to a comparatively undeveloped 6th district. centering on the exchange 66. The assessing arrangement shown in Fig. 5 is only suitable for trunks such as O--66 leading to a district comprising few exchanges. It will be seen that some of the exchanges have sub-exchanges located in different zones, for example 652, 656, 657. The selector circuits are modified so as not to be liable to false actuation when testing circuits over which booster impulses are passing. Specification 205,505, is referred to. First selector D, Fig. 2. The extension of a calling line to a selector D by the line switch C energizes the line relay 38 and release relay 39. The relapse of relay 38 in response to the first dialled impulse removes a short-circuit from relay 40, which becomes energized and connects itself in series with the vertical magnet 58, its own resistance being too high however to permit energization of the magnet 58. The re-energization of relay 38 at the conclusion of the impulse again short-circuits relay 40 so as to energize the vertical magnet, and this is repeated at each impulse. The relay 40, being slow to de-energize when shortcircuited, remains energized until the digit is completed and then relapses. The closure of an off-normal contact 57 at the first step energized a stepping relay 41, so that the relapse of relay 40 energizes the rotary magnet 60, which co-operates with the stepping relay in the usual way, each opening the circuit of the other alternately, to rotate the selector in search of an idle trunk. Every time it relapses, the relay 41 connects itself in series with the high-resistance switching relay 42, but if the trunk under test is busy the relay 42 is short-circuited by ground on the test wiper 63, and the stepping relay 41 is energized again to keep the selector moving. When an idle trunk is reached the relay 42 is no longer short-circuited and becomes energized, switching the connection forward to the repeater set 5. Fig. 3, and energizing relays 101, 102. It will be noted that the energization of the stepping relay 41 positively disconnects the switching relay 42, instead of merely short-circuiting it as in the usual arrangement. This is for the purpose of avoiding false actuation of the relay 42 in case two successive trunk are tested at moments when their test circuits carry metering booster impulses. Similar provision is made in the line switch C. Repeater E, Fig. 3. Relay 102 bridges the trunk 122, 123 through a repeating contact 112 of the line relay 101 and the upper winding of an electropolarized relay 105. During the passage of each set of impulses a relay 104 is energized, like the relay 40, Fig. 2, and provides the usual clean circuit for repeating impulses over the outgoing trunk. Assessing switch P, Fig. 3. Relay 104 also energizes, over circuit 125, the upper winding of a marginal relay 140. and closes a circuit 134 so that the first set of repeated impulses are repeated to the vertical magnet 161 of the switch P as well as over the outgoing trunk 122, 123. The relay 140 is at first only energized sufficiently to close the contact 146 in the circuit of its lower winding. While the relay 104 remains energized this winding is short-circuited over the wire 125, but when the relay 104 relapses at the termination of the digit the short-circuit is removed and relay 140 becomes fully energized, transferring the circuit 125 to the similar relay 141 and transferring the impulse circuit 134 to the rotary magnet 162, which is therefore operated by the impulses of the next digit, after which the relay 161 becomes fully energized and cuts the rotary magnet out of circuit. The wiper 163 is thus brought onto a terminal corresponding to the first and second repeated digits, i.e. to the exchange and sub-exchange through which the connection is extended subsequent to the exchange in which the trunk 122, 123 terminates. Metering. When the connection has been completed and the called subscriber has replied, the reversal of current in the trunk 122, 123 energizes the electropolarized relay 105, Fig. 3, which energizes relay 100, which locks itself and grounds the wire 172, so that the sluggish inter-acting relays 170, 171 become alternately energized and de-energized and a circuit is intermittently closed for the stepping magnet 176 of the common impulse switch D When this switch reaches the position shown it closes a starting circuit 133 to energize relay 143, which locks itself and connects relay 144 to the impulse wire 178. At each subsequent alternate step of the switch 1 the circuit 178 is grounded and relay 144 connects booster battery through a resistance 160 to the test circuit 84 to operate the meter M, Fig. 2. When the switch I reaches the contact wired to the selected terminal of the switch P it energizes relay 142, which locks itself and disconnects relay 144 from the impulse wire 178. The meter M is thus operated a number of times corresponding to the zone wire selected by the switch P. Preventing release of connection until metering is completed. This is effected by the relay 100 which locks the release relay 102 until the relay 142 is energised. When the calling subscriber disconnects himself, the relapse of relay 101 energizes relay 101 in series with relay 102. Relay 104 shunts a resistance 165 across relay 102, so that if metering has been completed relay 102 relapses, unlocking the various relays of the switch P and energizing the release magnet 164. Modified assessing arrangement Q, Fig. 5. In this arrangement, which may be used on trunks leading to a comparatively undeveloped district, such as the district centering on the exchange 66, Fig. 1, the two-co-ordinate switch P, Fig. 3, is replaced by a single co-ordinate switch 294, which responds to two digits in turn and controls a group of relays 256 - - 260. Assuming that a call is being made to the exchange 65, Fig. 1, the d git 5 operates the switch 294 to energize relay 256, which connects the circuit 250 of the metering cut-off relay 253 to the 11th wire 191 of the impulse switch I, corresponding to the fact that the exchange 65 is in the 11th metering zone from the originating exchange O. At the termination of the digit the magnet 290 is energized to restore the switch 294, but relay 256 remains locked. If the connection is further extended to the sub-exchange 657 the next digit 7 operates the switch 294 to energize relay 257. which transfers the circuit 250 to the 10th wire 190, corresponding to the fact that the sub-exchange 657 is in the 10th metering zone, and when the called subscriber replies, ten booster impulses are transmitted to the meter. Or if the call is extended to either of the sub-exchanges 652 or 656, which are in the 12th metering zone, the digit 2 or 6 will energize relay 258 to transfer the circuit 250 to the 12th wire 192 of the switch I. Similarly, if the call is to the exchange 66 in the 10th zone, relay 259 is energized to select the 10th wire 190, and if the call is to the sub-exchange 669 in the 11th zone, relay 260 is subsequently energized to transfer to the 11th wire 191. Metering duration of conversation. The energization of relay 253, Fig. 5, when the first complete charge has been recorded on the meter, connects the circuit 250 to wire 326, 133 to 328, and 178 to 327. When the switch I commences its next cycle, relay 344 is energized over circuit 133, 328 and locks itself up, connecting the impulse circuit 178, 327 to the steping magnet 340 of a switch T, which is thus stepped forward at every alternate step of the switch I. When the switch 1 reaches the circuit such as 190 selected by the relays 256 - - 260 a circuit 190, 250, 326 is closed to short-circuit and unlock relay 344, which stops the switch T. During succeeding cycles of the switch I these operations are repeated, the switch T being thus advanced, as long as conversation continues, at an average rate corresponding to the original charge assessed. Once in every cycle of the switch T a circuit 329 is closed to energize relay 255 which transmits an additional booster impulse to the meter. On the release of the connection a circuit 325 is closed to