Patent GB-253986-A (GB)
Title: Improvements in or relating to telephone systems
IPC: H04Q3/00
Filed: 1925-03-20
Abstract: 253,986. Automatic Telephone Manufacturing Co., Ltd., and Ostline, J. E. March 20, 1925. Addition to 238.477. Automatic and semi-automatic exchange systems.-In a repeater of the kind described in the parent Specification, in which busy flash signals are repeated by intermittently preventing the flow of the current fed back over the speaking leads in series, a relay controlled over the. outgoing trunk conductors causes battery and earth to be connected alternately to an incoming speaking conductor, in the repeater itself without any external connections to interrupters. The bridged relay may also be arranged to test the continuity of the outgoing trunk immediately it is taken into use, and if it is faulty cause a number unobtainable tone to be connected to the calling line. Further, this relay may initiate the release of the preceding switches and then render the repeater non-selectable until the fault is cleared. In another modification, additional provision is made whereby when a faulty trunk is encountered beyond the repeater, an alarm is given, and the switches held up until manually released by an exchange attendant. Fig. 1 shows a repeater arranged to repeat busy signals without any connections being made over external leads to common interrupters. When the repeater is taken into use, the line relay A closes a bridge across the outgoing conductors 30, 31 including relay G and the right-hand winding of polarized relay D. Relay G only responds, and energizes a relay H, which closes a circuit for the release relay B, which in turn earths the release wire 3 and energizes the polarizing winding of relay D. On the transmission of impulses, the de-energizations of the line relay A open at armature 16 the loop across the outgoing trunks 30, 31, the first relapse closing a circuit for slow-release relay E, which completes a more direct bridge across the trunks 30, 31. When the called party replies, the current reversal over the back-bridge causes the response of the polarized relay D, which energizes the usual supervisory reversing relay C. Assuming that at some stage in the connection all the outlets are found busy, alternate battery and earth as well as busy tone are connected to the lower trunk 31 in the manner described in Specification 250.694. If the call is from a subscriber he will hear the busy tone, whereas if the call is from an operator, a flashing signal will be repeated back in the following manner. The intermittent battery on the trunk 31 causes an intermittent cessation of current flow over the leads 30, 31 and an intermittent relapse of relay G, which opens the circuit of relay H, which in turn energizes the slow release relay F. The relay F therefore intermittently applies battery through the resistance r and the lower winding of relay A to the line conductor 2 in place of earth at armature 25. To ensure a true reproduction of the flashing current in spite of the slow action of relay F, which is arranged to hold release relay B during the resultant relapses of relay A, during the relapse of relay F the conductor 2 is earthed over armature of relay H. The relay F when energized short-circuits the impulse contact 16 to prevent the release of the connection owing to the intermittent relapse of relay A. According to the modification shown in Fig. 2, number obtainable tone is transmitted and the repeater is made non-selectable if the outgoing trunk is faulty. When the repeater is taken into use, the line relay A<1> energizes the release relay B<1>, which earths the release wire 52, closes a bridge through relays G<1>, D<1> across the outgoing trunk conductors 85, 86, and energizes the other winding of relay D<1>. The relay G<1> energizes relay H<1>, which locks up and disconnects alarm signal and number obtainable tone leads SE, NUT. Relay A<1> repeats incoming impulses, the relay E<1> responding at the first and closing a more direct bridge across the conductors 85, 86. If a busy group of trunks is encountered, battery and earth are alternately connected to the lower conductor 86 causing the intermittent relapse of relay G', which closes the circuit of relay F'. Relay F<1> intermittently connects battery to the incoming trunk conductor 51 over the lower winding of line relay A<1>, and holds the release relay B<1> over its upper winding. If the outgoing trunk 85, 86 is faulty, relays G<1>, H<1> do not respond when relay B<1> first energizes, and a circuit 63, 59, 67 is closed for relay F<1>, which lights a supervisory lamp L, earths the release wire, locks over the alarm wire SE, and connects NUT tone to the lower trunk 51. The calling party on hanging up releases relays A<1>, B<1>, but the release wire remains earthed by relay F<1>. Between the relapse of relays A<1>, B<1>, the relay E' is momentarily energized, and being rendered slow to release by its short-circuited upper winding, causes the holding earth at armature 66 to be removed from the release wire 52 for a moment after the relapse of relay B<1>, thereby releasing the preceding switches. When the fault is cleared, the relay F<1> is unlocked by the attendant and the repeater rendered selectable. The junction 85, 86 is accessible to local switches over conductors 87 - - 89. In the further modification shown in Fig. 3, the arrangement is very similar to the preceding modification, but provision is also made whereby an alarm is given and the switches held up if a faulty trunk is encountered after the first trunk has been taken into use, and whereby the annoying click in the calling party's receiver is reduced when the reversing relay C<2> energizes. The operation of the repeater is substantially the same as in Fig. 2, when the outgoing trunk 134, 135 is not faulty, when it is faulty, and when a busy group of trunks is encountered, with the exception that in the first case the relay H<2>, which is energized by the response of relay G<2>, prepares a circuit so that when the relay C<2> pulls up on the reply of the called party, a resistance r<3> is connected across the windings of the line relay A<2> to reduce the click and to prevent this relay from tending to release. Further, if a faulty trunk is encountered at a switching stage subsequent to the trunk 134, 135 being taken into use and after the relay H<2> has locked up, relay G<2> falls away energizing relay F<2>, and a circuit 114, 108, 116, 122, 130 is closed for a dash-pot relay DPR, which is arranged not to respond to the brief closures of its circuit which take place when the relay F' is intermittently energized to repeat busy flash current in the event of a busy group of trunks being encountered. In this instance, however, the relay DPR lights an alarm lamp L<2> and closes an alarm circuit over conductor SE". Should the calling party hang up, relay A<2> relapses, and a locking circuit 109, 113, 120, 126 is closed for the release relay B<2>. which holds the switches until it is manually released by an attendant.