256,300. Standard Telephones & Cables, Ltd., (formerly Western Electric Co., Ltd.), and Chanter, A. J. April 8, 1925. Automatic exchange systems.-In a registercontroller sender in which means are provided for testing the sender impulse springs, the distributor switch which steers the dialled digits to the different component registers is adapted to be advanced to a position in which it prepares an alarm circuit in the case of zero calls as well as ordinary calls. The invention is described as applied to a register sender, the sending switch SS of which is driven by impulses from interrupter springs MS, whilst the transmitted impulses are generated by interrupter springs LS. Both these interrupter springs MS, LS are tested in position 2 of the digit distributing switch DD after the first dialled digit has been received by the register sender and if either or both are not functioning properly, the register sender is disconnected and restored, and an alarm is given. In order that this test shall also be operative without delay in zero calls when the register sender functions in a special manner responsive to a reversal of the loop to it, provision is made whereby in such calls the digit distributing switch DD is automatically driven to position 2 on the register sender being taken into use. Test of impulse springs of register-controller. The impulse relay A closes a circuit for the time pulse relay TP over the time pulse conductor TPW, and energizes relay B which grounds the private wire PW, energizes the left-hand winding of relay D, Fig. 2 (which normally does not pull up since its other winding is energized in opposition over the outgoing impulsing loop), and grounds the impulse motor start wire MSW to start the impulse springs interrupting in a circuit including the lower winding of two-step relay LC. Relay LC pulls up its light armature when the springs LS close and fully energizes when they open, thereby lighting a supervisory lamp Lover grounded wire SGW, grounding the strapped contacts in the bank 1 of the sending switch SS, and completing a circuit for the lower winding of two-step relay CC over wiper 4 of the sending control switch SC and the magnet interrupter springs MS. When the springs MS close, relay CC closes its half-step contacts, and when they open, fully energizes over both windings and closes a circuit for magnet R7 which moves the switch SC to position 2, thereby de-energizing relay CC. If either set of impulse springs LS, MS is not functioning correctly, the control switch SC is not moved out of its first position. When the subscriber dials, or when in the case of a zero call the out-impulseing loop is reversed, the digit distributing switch DD steps to position 2 and relay DS relapses, as described in later paragraphs. A circuit is thereupon closed over wiper 2 of switch DD and wiper 3 of switch SC for a pulse alarm relay PA, which locks up over key BL, lights lamp L, grounds an alarm wire SFW, earths the private wire PW, and energizes a relay M. Relay M breaks the out-impulsing circuit and a statistical metering circuit, grounds the pulse wire to disconnect the register-controller, and energizes relay CO, which causes the register-controller to restore as described subsequently. The relapse of relay B is followed by the deenergization of relays M,A, CO. Ground is then replaced on the private wire over contacts 10, 11 of relay PA and holds the register-controller busy until the busy key BK is thrown and the relay PA unlocked. Setting of register-controller. The " B " and " C " digits are repeated by relay A to the vertical and rotary magnets V, R1 of the exchange code register over wiper 10 of switch DD in positions 1 and 2 respectively. Series relay C pulls up at the beginning of each digit and energizes a relay DS, which connects interrupted ground on lead IGW to the lamp L in place of permanent ground on lead SGW. At the end of each impulse, relays C, DS relapse in succession to give an impulse to the stepping magnet R2 of the digit steering switch DD. In like manner the numerical digits are recorded on registers MR, CR, DR, UR in positions 3 to 6 of the switch DD. Transmission of office code. In position 3 the. switch DD grounds wiper 2 of the sending control switch SC, and over wiper 4 of this switch (in position 2) grounds spring 1 of the interrupter springs MS, the other spring of which is connected to relay CC, which pulls up in two steps as previously described and locks up over wiper 4 of switch SC. Relay CC extends the interrupter circuit over springs MS to the stepping magnet R8 of the sending switch SS, on the first step of which relay SA is energized, removes a shunt from the out-impulsing springs LS, and short-circuits the right-hand winding of relay D. Impulses are thus sent out over the loop until the switch SS engages the contact marked by wiper 1 of the code register W over the translating frame, whereupon a stop relay SZ pulls up, locks to ground at armature of relay SA, unlocks relay CC, shunts the impulse springs LS, energizes the back-stroke stepping magnet R7 of the control switch SC, and closes a restoring circuit for the sending switch SS. When the latter switch reaches normal, relays SA, SZ relapse and the control switch SC is driven to position 3. The remaining five routing digits are set in a similar manner in positions 3 to 7 of the switch SC. Transmission of numerical digits; preventing transmitting mechanism from catching up, registering mechanism. The numerical digits are transmitted in the same manner as the routing digits in positions 8 to 11 of the control switch SC. The ground for starting the sending switch SS for sending a numerical digit is derived from an off-normal arc of the succeeding register, so that the transmission of any digit is held up until the next is dialled. Release of register-controller; statistical metering. In position 12 of the control switch SC the wire MW is grounded to energize a recording meter and relay CO energized. Relay CO locks to the private wire, and de-energizes relay B,. which opens the incoming impulse circuit, unlocks relay LC, and completes restoring circuits - over the upper winding of relay RA for the code register and the numerical registers. When the switch DD reaches normal, restoring circuits are closed for switches SS, SC over the lower wind. ing of relay RA. Relay RA grounds an alarm wire RAW and holds the register-controller busy until all the component switches are restored. Routing code with lees than six digits. Wipers, for example 5, 6, of the code register W not required, are connected to a skip contact DCO so that the control switch SC in positions 6 and 7 completes a self-interrupting circuit over the lower winding of relay RA. Relay RA opens the locking circuit of relay CC which prevents the operation of the sending switch SS during the advance of switch SC to position 8. Dialling non-existing exchange code. Spare terminals on the exchange register W are jumpered to contact SN so that relay M energizes, grounds the pulse wire PSW to disconnect the register-controller, opens the statistical metering circuit and the out-impulsing loop, and energizes relay CO, which causes the register-controller to restore as previously described. Subscriber fails to dial " B " digit or dials an incomplete number. Ground on the pulse wire TPW causes a two-step relay TP to close its light armature contacts 5, 6, and when the ground is removed relay TP energizes fully, and unless it is unlocked by the operation of relay A by the first or next digit before the impulse wire is next grounded, the relay M is energized and restores the register-controller as described in the preceding paragraph. Call to coder call indicator. In this case it is necessary to hold up the register-controller positvely between two digits until two successive hunting switches have functioned and a free coder has been found. After the sending of one digit the current over the out-impulsing loop and over the right-hand winding of relay D is reversed, the relay D pulls up, and the stop relay SZ is held over wiper 3 of the control switch SC until a free coder is found, when the loop current is reversed back to normal and the relay D relapses. Non-numerical calls, e.g. TRUnks, TOLI, COMplaints. When the code necessary to route the call to an operator has been sent, a contact OC on the jumpering frame is earthed over the contact engaged by the next operative wiper of the exchange register W, so that the relay CO is energized and released the register-controller as previously described. Call to enquiry operator by dialling digit " 0." The register-controller leads from the tenth level of the " A " digit switches are reversed, so that when an idle register-controller is engaged and its relay B energized, the relay D also pulls up and closes a circuit for relay MB. Relay MB holds over contacts of relay B, energizes vertical magnet V of the code register W in series with relay C which energizes relay DS, grounds the private wire PW and wiper 2 of the control switch SC, shunts the right-hand winding of relay D, and connects wipers 1 to 5 of the code register to five jumpered contacts on the distributing frame and the wiper 6 to contact OC. Relay D relapses and between the consequential relapse of relays C, DS, an impulse is sent to rotary magnet R2 which steps switch DD to position 2 in which the interrupter springs LS, MS are tested as previously described. Meanwhile, if these springs are functioning properly five routing digits are sent in the usual manner, after which contact OC is grounded over wiper 2 of switch SC in position 7, and the relay CO is energized to release and restore the register-controller. Specification 256,295 is referred to.