Patent GB-191518084-A (GB)
Title: Improvements in Telephone Systems.
Inventor: TURNER HUBERT SYDNEY
IPC: H04M3/523
Filed: 1915-04-30
Abstract: 18,084. Turner, H. S. June 20, 1914, [Convention date]. Exchange systems.-The calling-line is indicated by the glowing of a lamp in the usual way, but the pilot signal consists of an audible signal in the operator's receiver, which continues until the call is answered. If the operator is busy or absent, the pilot signal is transferred to an adjacent operator. The tone of the pilot signal for each operator is different, so that an operator can distinguish a pilot signal for her own position from one originating at an adjacent position. An audible disconnect signal is produced in the operator's receiver when an idle cord-circuit should be taken down. The calling-subscriber's line relay is energized by a pulsating current so that a tone signal is produced in his receiver until the operator answers the call. In the Figure, all apparatus common to one operator's position is shown above the cord circuit and between the dotted lines. All apparatus common to the left and right adjacent operators is shown to the left and right of these dotted lines respectively. Calling-line and pilot signals; audible signal to calling-subscriber. When the subscriber A removes his receiver, his line relay H is energized by current from the battery K through an interrupter I shunted by a resistance i<1>, and closes the circuit of the line lamp h<1> through the primary h<5> of the operator's induction coil, pilot relay L, and the shunted interrupter 1. If the operator is free, the currents induced in the secondary of the coil pass to her telephone m<4> over contacts m<1>, m<8> and the normal contact of relay M. In the arrangement shown, the line lamps are divided into left and right hand groups, having separate pilot circuits, of which one is fully shown and the other is represented by the primary h<5>. This arrangement is adopted in order that, when the operator is busy, in which case the relays L, M are both energized, calls on the left group may have their pilot signal transferred in the first place to the left adjacent operator and then, if she is busy, to the right-hand operator, while the signals of the calls in the right group may be transferred first to the right-hand operator and to the left. If an operator leaves her position, she removes the plug m<3> of her receiver and sets the manual switches l<1> so as to transfer the pilot signals, both those originating at her position and those transferred from another position, to one or both adjacent operators. The arrangement of one winding of the pilot relay L in the circuit of the primaries h<5> ensures that the pilot signals originating at an operator's position have precedence over those transferred from another position. Connexion of operator's speaking set to calling-line. In response to the line signal h', the operator inserts the answering-plug N and grasps the calling-plug N' in such a way that a finger-contact m<7> worn by the operator engages a thimble n<1> on the calling-plug; thereby completing a circuit from the battery lead k' through the right winding of the pilot relays L, M, contacts m<7>, n<1>, finger-contact relay P, sleeve of plug N, and cut-off relay G. The relays L, M disconnect, and prepare for the transfer of, the audible pilot signals, as previously described, and, in addition, the relay M closes the circuit of the operator's microphone m<11> and immediately afterwards completes the connexion of the operator's telephone m<4> through a condenser m<9> to the armatures of relay P, which connects them to the right windings of the repeater U, U<1>. The relay P also closes a circuit for the supervisory relay T over the calling-line; the relay T then closes a fresh circuit for the cut-off relay G through the answering-relay S and the supervisory lamp t'. The relay S (1) connects the left windings of the repeater U, U<1> to the calling-line, (2) connects the relay T directly to the battery instead of through the interrupter Q, and (3) bridges the non-inductive resistance t<2> across the relay T. The calling-line and the operator being now connected through the repeater U, U', the subscriber, as soon as the tone in his receiver ceases, tells the operator the connexion required. The busy test of, and the supply of ringing- current to, the wanted line are effected in the manner described in Specification 6480/15. Talking circuit and supervisory signals. The relay O, energized by the relay T<2> when the called subscriber answers, (1) connects the called station to the coils of the repeater U, U', (2) bridges the relay T<2> by a non-inductive resistance t', as at the answering side of the cord, (3) connects the relay T<2> direct to the battery K, and (4) disconnects the relay P. During conversation, the relays Q, S, T, T<2> are all energized, and the supervisory lamps t<1>, t<4> glow. Automatic disconnexion of cord circuits. When either subscriber hangs up, his supervisory relay T or T<2> is de-energized and opencircuits the corresponding relay S or O, which isolates the associated plug, so that the respective subscriber's cut-off relay de-energizes and the subscriber can at once initiate or receive a further call. The supervisory lamp t<1> or t<4> also ceases to glow. When both subscribers have replaced their receivers, a circuit is closed through the disconnect relay P<1> over the back contact of relay S, ringing-relay Y, back contact of relay O, and cut-off relay G<1> of the called subscriber. The resistance of the relay P' is such that the relays Y, G<1> are not energized, but the relay P' closes the primary circuit of the disconnect transformer P<2>, so that the operator receives an audible signal, distinct from the pilot signals, advising her that the cord circuit should be taken down. The disconnect signal, unlike the pilot signals, is not transferable to adjacent positions.