Patent GB-202425-A (GB)
Title: Improvements in or relating to telephone circuits
IPC: H04M15/30
Filed: 1922-05-23
Abstract: 202,425. Anderson, T. G., and Huntsworth, G. H. May 23, 1922. Manual exchange systems; metering.-In a central battery system, the calling subscriber operates a switch j<2> to connect his instruments across the line, certain contacts h, h<2> being restored by a time relay f after an interval to connect up a release magnet e', this being prevented in the case of a successful call by the operation of a metering switch j<5>, connecting across the line the metering magnet b<1>, which disconnects itself and re-establishes the instrument circuits. Calling. On removal of the receiver and operation of the switch j<2>, contacts h, h<2> and a group of contacts K are actuated, closing a local circuit for the receiver R and bridging the transmitter T across the line in a circuit A, m<5>, k<4>, c<1>, v, k<8>, h<2>, T. Alter 15 seconds, the contacts h<2> are opened by the time switch f cutting out the transmitter, and after a further 20 seconds the contacts hare closed, connecting across the line the release relay e<1> (e<1>, h, k<6>, m<2>, k<4>, m<5>, A), which attracts its armature e<3> to restore the contacts K and cut out the receiver. If the call has not been answered within the time, the switch j<2> must 'be operated again. When the connection has been obtained, the subscriber operates the metering switch j<5>, actuating contacts M, connecting across the line the meter magnet b<1>, (b<1>, d, m<4>, A), which attracts its armature b<3>, and operates the meter band contacts d. The metering circuit is thus broken, and the transmitter is bridged across the line (A, m<4>, d, k<4>, c<1>, v, m<6>, T) with a release magnet e<9> in parallel, which serves to clarify speech by absorbing current fluctuations due to the condenser Q. The release magnet e<9> energizes when the parallel circuit through the receiver is broken at the switch hook, attracting its armature e<11> and restoring the contacts K. M. d. Receiving a call. On energization of a ringing relay r, the armature r opens contacts v and releases a member r<5> to close contacts s, t, thereby connecting across the line a relay n (n, t, k<1>, m<5>, A) whose armature n<6> is controlled by a time device, n<9> and closes contacts p after 35 seconds to operate the release magnet e<1>. This is prevented by lifting of the receiver and operation of the switch j<2>, cutting out relay m and connecting up the transmitter (T, s, k<8>, v, c<1>, k<4>, m<5>, A). The release magnet e<1> is connected up in parallel after 35 seconds over the contacts h and serves to clarify speech, and operates upon hanging up to restore the contacts K, s, t. Release of switches from the exchange. If the receiver has not been replaced and one or both of the switches i<2>, i<5> are in operative position, they may be restored by ringing current from the exchange, operating the relay r and breaking the transmitter circuit at the contacts v, thus energizing one of the release magnets e<1>, e<9>. Preventing misuse. The lever f<6> of the time switch f is depressed by a pivoted catch f<10> on the spring-controlled operating plunger f<15> of the switch j<2>, the catch being removed from action at the end of the stroke by a guide f<21>. In addition, operation of either of the switches j<2>, j<5> depresses an arm f<30> in a slot by means of engaging levers f<3>', f<31> or f<38>, f<31>, thereby moving forward a member f<22> through a spring f<29> to remove the catch f<10> from action and prevent depression of the plunger f<15>. Interference with the operation of the time switch f is thus rendered impossible.