Patent GB-408286-A (GB)
Title: Improvements in or relating to automatic or semi-automatic telephone systems
IPC: H04Q3/42
Filed: 1932-10-06
Abstract: 408,286. Automatic exchange systems. STANDARD TELEPHONES & CABLES, Ltd., HARTLEY, G. C., and SNELL, M. S., Connaught House, Aldwych, London. Oct. 6, 1932, No. 27754. [Class 40 (iv).] In a group of switch circuits involving a common multiple wire connecting a set of contacts, comprising similar selectable contacts in each circuit, to another set of contacts comprising similar contacts in each of said circuits or in a different group of circuits, incorrect action due to the simultaneous operation of two or more circuits is avoided by arranging that only one circuit at a time can use the multiple. A similar arrangement is used where a relay is connected in multiple to a selectable contact in each of the switch circuits and controls contacts individual to or directly connected to the switch circuits. The invention is applicable to by-path systems in which a group of conversational switches is associated with three or more by-path circuits or to P.B.X or dead line discrimination where discriminating relays are connected to the multiples of first and last contacts of P.B.X groups or to a multiple connecting dead contacts. These discriminating arrangements may be applied to final selectors, but are described in detail in connection with a group of final by-path circuits. Forced release is applied to a circuit at the end of a predetermined period after seizure, but when a circuit has taken the common multiple into use, forced release is applied after a considerably shorter period. In the by-path system shown in Fig. 1, conversational switches S1, PS of the first and penultimate stages are controlled by single by-path circuits BP1, BP2, but each stage may be associated in known manner with two by-path circuits taken into use alternately, the conversational switches being connected in reverse order in the banks of the two R1 switches and the test potentials of the two marking circuits being of opposite polarity. At the final stage, the conversational switches FS are associated with three or more by-paths. At the first group selecting stage, the by-path switch hunts for an idle conversational switch associated with an idle by-path at a succeeding stage, while at the penultimate stage, the by-path switch hunts for an idle final by-path and the conversational switch hunts for an idle final conversational switch. The bank multipling of the final by-paths and between the by-paths and the conversational switches involves the common multiples described above, including P.B.X and dead number discrimination, and immediately after the tens digit has been transferred from FR1 to FR2 in known manner, the final by-path tests the multiple. If or when the multiple is idle, FR1 hunts for the final conversational switch selected by the penultimate stage. The first stage gives access to five two-thousand groups and sends forward a signal if the thousands digit is odd. The second stage gives access to ten two-hundred groups in accordance partly with the hundreds digit and with the said signal, while it sends forward a signal if the hundreds digit is even to enable the final stage to make a selection from 200 lines. The wiper switching relay of the final conversational switch busies the switch when taken into use until it is determined whether or not wiper switching is required, the switch being subsequently busied in the usual manner. Penultimate stage, Fig. 2. An idle conversational and by-path circuit is found in known manner by battery over wipers rm21 and rm15 (both normal) and wire T. Impulse relay A pulls up followed by B, BB, and if this digit is odd, relay J is operated from the first by-path. Relay A repeats the hundreds digit to RM1 and RM2 steps on until its circuit is opened by relay M on reaching the first contact of the group marked over rm10 or rm19 (dependent on relay J). When C falls back at the end of the digit, EH pulls up, locks and operates E which releases M. Relay JA is operated if the hundreds digit is even (for discrimination at the final stage) and J falls back since both its local circuit and the operating circuit from the preceding stage are now open. Switch RM2 hunts for an idle outlet (by-path only) under the control of P, while RM1 hunts for the seized conversational switch under the control of T. Relay P operating to an idle final by-path energizes H which locks up, stops RM2, releases EH and extends the impulse circuit to rm25. Relay T operating over the seized conversational switch S energizes TT which releases P so that the switch hunts until it reaches the first contact of the group corresponding to the seized final by-path, whereupon M pulls up over rm10, sm4, rm21. Relay EH pulls up, locks and releases M so that SM hunts for an idle final conversational switch in the group until P operates over rm16, sm3 to battery at the final switch. Relay E, being short-circuited, falls back, and wiper-switching JS in the final switch pulls up over the upper speaking wire, rm18, rm20, and opens the test-circuit. Final stage, Fig. 3. If JA, Fig. 2, has been operated (hundreds digit even), J at the final stage is energized. Relay BB also operated when the final by-path was seized. The tens digit is repeated by A, Fig. 2, to RM1, Fig. 3, and RM2 steps on to the group marked by RM1 whereupon M pulls up, stops RM2 and operates E to transfer the impulse circuit to RM2 which is stepped by the units digit, M being released when RM2 takes its first units step so that CE (lower) now pulls up in series with E and locks. At this point in the operations (units digit coming in and final conversational switch seized from the preceding stage) a test is made for the idle condition of the common marking multiple. Relay PF (no longer short-circuited by CE) operates over rm20, Fig. 2, and the previously described circuit to JS, Fig. 3, and connects relay P to battery over a resistance RS common to the group of final by-paths. If or when no other by-path is using the common marking multiple, P operates over both windings in series and connects ground over its low resistance lower winding to resistance RS to busy the multiple to other by-paths. Relay P also completes a stepping circuit for RM1 and at p1 operates QP, Fig. 2, which prepares a circular test circuit from p1, Fig. 3, over rm28, Fig. 2, rm17, sm2, lower speaking wire, rm10, Fig. 3, relay M to battery. When RM1 reaches the final switch, M operates and energizes TT which locks up, releases M and connects marking ground from p1 to marking bank rm23 or 24 dependent on JA. The conversational switch now hunts for the marked line under the control of M which pulls up over rm10, sm7, rm23 or 24 to ground at p1 when the line is found. Relay TU now pulls up and shortcircuits PF which disconnects the multiple rest-relay P, but the multiple is held busy at tu6. The set of wipers to be used in the final conversational switch depends on relay JS which, it will be recalled, was operated in series with PF. The continued operation of JS, after the operation of TU, depends on relay J which was operated if the hundreds digit was even. Wanted line idle ; completion of connection. The relapse of PF restores E which connects P (upper) over rm19 to the cut-off relay of the wanted line. If the line is idle, P operates and locks up over its lower winding since W has meanwhile been energized and G in the penultimate by-path operates to ground on rm18, Fig. 3, which is also connected over rm19 to operate the cut-off relay. Ground from p1 operates the switching relay HS and also, over rm26, Fig. 2, energizes JS, GS in the penultimate conversational switch, continuous ringing being connected up by GS until B in the by-path falls back to operate BS whereupon BDS switches over to intermittent ringing and releases T so that TT, BB falls back and both penultimate and final by-paths release. On reply of the called party, FS, FFS pull up, DS operates over the loop, GS, JS fall back in turn and a booster metering impulse is connected to wire H. Busy signals. If all the final by-paths or final conversational switches are busy, M, Fig. 2, operates over the last contacts of groups in rm22 or sm4 and energizes G since the test relay P is not operated. Relay TT will be operated as previously described and consequently B falls back and BS, BDS pull up as in the precedi ng paragraph and the by-paths are released, but since GS is not operated, busy tone is sent back from BF. If the wanted line is busy, W, Fig. 3, is operated as before, but P remains inert so that G, Fig. 2, pulls up to initiate the transmission of busy tone as before, since GS is not operated. Dead numbers. Dead terminals in banks rm25-28 of the final by-path are multipled to relay NU common to the by-paths so that on selection of such a terminal, NU opens the circuit for testing the wanted line and connects ground from a common lead to rm27, Fig. 2, to operate J. The contacts of NU may be common or individual to the by-paths and more than one relay may be used. Relay G operates as for a normal call so that ground is connected to rm14 to GS, JS of which only JS energizes. Relay G also releases B whereupon BS, BDS pull up and release the by-paths as above, but NU tone is now sent back. Forced release. A pulse over lead A operates ZA which holds over its lower winding dependent on BB which falls back when the by-paths are released. If ZA is still operated when the pulse over Z arrives, G and J are operated in parallel, E pulls up, RM1 will step on to the conversational circuit if it has not already done so, JS pulls up with results as described in the preceding paragraph, and NU tone is sent out. The A and Z pulses give release after 20 seconds, but pulses over P, Q are substituted while the common multiple is actually in use so as to force release after four seconds. When the multiple is seized, P, Fig. 3, and QP, Fig. 2, are operated and the latter relay connects pulse lead P to JA which, when operated, connects pulse lead Q to r