Patent GB-418787-A (GB)
Title: Improvements in or relating to automatic or semi-automatic telephone or like systems
IPC: H04Q3/00
Filed: 1933-11-24
Abstract: 418,787. Automatic exchange systems. STANDARD TELEPHONES & CABLES, Ltd., WRIGHT, E. P. G., HARTLEY, G. C., and BRAY, F. H., Connaught House, Aldwych, London. Nov. 24, 1933, No. 32849. [Class 40 (iv).] In a final selector adapted for P.B.X. hunting and controlled by a marking switch which marks the lines of a group in succession, the selector and marking switch advancing alternately, the positions of the marking switch which correspond to unnumbered P.B.X. lines may correspond also to dead or changed numbers, and are then wired in such a way that in response to such numbers, NU tone is sent or the call is routed to an operator. The 200-point final selector described forms part of a byepath system of the kind described in Specification 408,286 in which the operations at the final stage are in part controlled by relays at the penultimate stage. Call to an individual line. The first numerical stage gives access to 2000-line groups, and a discriminating signal is sent forward if the thousands digit is even. In the penultimate byepath, Fig. 1, relays A, B, BB, D energize, and the discriminating signal operates JD, J. The hundreds digit sets the switch R1, and the switch R2 takes up the position marked over rm19 or 10 according as J is operated or not. Relay EH pulls up and R2 hunts for an idle outlet. Relays P, H energize, disconnecting D, EH, and the impulse circuit is extended over rm25 to the magnet of the switch FR1, Fig. 2, in the final byepath, while earth on rm20 connects up BB, Fig. 2. Consecutive odd and even hundreds digits produce similar marking effects, and if the digit is even, earth is connected over rm18, rm26 to operate J, Fig. 2, which controls wiper-switching at the final stage. Relay E energizes and R1 connects to the chosen penultimate selector S, which moves to the group marked over rm21 and then, EH being up, hunts for an idle final selector, when P energizes. The first numerical byepath is released. The tens digit sets FR1, Fig. 2 and FR2, Fig. 3, takes up the marked position, and MF, Fig. 1, pulls up. Relay TD transfers the impulse circuit to the switch FR2, and if the tens digit is even JA energizes and switches over the wipers of FR2. Relay UD, Fig. 2, energizes during the units train and connects up X which seizes the common marking multiple. The switch FR1 connects to the chosen final selector FS and the latter advances to the position marked by FR2, when MF pulls up over rm27. Wiper-switching relay JS, Fig. 2, energizes if J is up. If the wanted line is idle, QF energizes over rm26, UD, Fig. 1, being up at the end of the tens digit, connecting up HT and switching relay HS of the final selector. Relay G energizes, disconnecting B, H to release the final byepath, but the penultimate byepath is held by T until BDS operates in the selector. Relays GS, JS pull up, followed by BS, BDS and ringing current is applied, first continuously from wire CRL and then intermittently from IRL. Upon reply, FS, FFS, DS energize and metering takes place in the usual manner. If the line is busy, QF, HT, GS, JS do not operate, and BDS sends back a busy signal from wire BUL. Dead numbers. A common relay NU, Fig. 3, is multipled to positions corresponding to such numbers in banks frm27-20 of all the byepath switches FR2. With X, Fig. 2, up, NU energizes, opens the test circuit and connects earth over rm25 to operate J, Fig. 1. Relay GS energizes, but not JS, so that BDS sends back NU tone from wire NUL. Changed numbers. The corresponding positions are multipled to a common relay CN which operates in the same way as NU and marks an arbitrary line in the bank of the final selector to route the call to an operator, who informs the calling subscriber of the change and completes the desired call. P.B.X. hunting. The first lines of P.B.X. groups are marked by full earth in banks frm27-20, causing operation of V, Fig. 2 and V, VR, Fig. 1, and MF is connected over rm24 to one of wipers frm23-26. Each line of the group is marked in bank frm21 or 22, and each marking wire except the first is continued to the terminal of the next preceding line in one of banks frm23-26. The lines of a group may be distributed in the odd and even hundreds group and in odd and even tens groups, and accordingly relays ET, OT, EH, OH are provided to take care of wiper-switching in the switches FS, FR2. Assume that all lines of the wanted group are busy. Test relay QF fails to operate on the first line and FS steps to the second, when MF pulls up over frm23, b, a. A further test is made, and QF still being inoperative, MFR energizes and completes a circuit over rm28 for stepping FR2 to the second line, when MX energizes over rm27, frm21, a, and disconnects MF, MFR. The third line is now marked over frm23, d, c and FS moves to this line, whereupon FR2 steps again. In position g, j of FR2, frm22, 24 are to be effective, consequently in the preceding position e, h, ET energizes over frm27 and connects up JA, which locks. In position m, n, a change from the odd to the even hundreds group takes place, so that in the preceding position k, l, EH energizes and connects up J, which locks and operates JS. In the same way, with the connections shown, OT energizes in position o, p and disconnects JA, while OH energizes in position q r and disconnects J, JS. On the last line, Z energizes in series with MF and connects up G over wiper rm25, and a busy signal is sent. If an idle line is found, QF energizes and the connection is completed as in the case of a call to an individual line. When positions corresponding to dead or changed numbers are used to mark unnumbered P.B.X. lines relays NU, CN are ineffective since relays V, Figs. 1, 2, are up.