Patent GB-180330-A (GB)
Title: Improvements in or relating to telephone systems
IPC: H04Q3/00
Filed: 1922-05-17
Abstract: 180,330. Automatic Telephone Manufacturing Co., Ltd., (Assignees of Wicks, J.). May 23, 1921, [Convention date]. Addition to 158,276. Automatic exchange systems; coin-freed and metering systems.-Relates to systems of the kind described in the parent Specification in which a coin-freed substation may set up a privileged connection (e.g. to a recording operator) without the insertion of a coin, but when connection with an ordinary subscriber is attempted the completion of the connection is prevented unless a coin is inserted. The present invention relates to the following features :-(1) The recording operator is given a discriminating tone to inform her as to the class of service to which the calling subscriber is entitled; (2) the calling subscriber must insert the coin before commencing the call to an ordinary line; (3) alarm and supervisory signals indicate when the coin-collecting mechanism or the batteries operating it are out of order; (4) each line is provided with a meter to check the collection of coins; (5) a polarized reversing relay in the repeater ensures that the connector is not held up if the called subscriber replaces his receiver first. In the system described, a subscriber A, on removing his receiver, is connected through a line switch C and repeater D to a first selector E<1>. Connection can be set up without fee through special second selectors E<2> to a record operator O or other privileged station, or on payment of a fee over selector E<3> and connector H to an ordinary subscriber A<1>. If no coin is inserted and an attempt is made to call an ordinary subscriber A<1>, when connection is extended to a second selector E<3> the contact 184 of the repeater line relay 135, Fig. 2, is short-circuited by a relay 141 so that further impulses are ineffective. The relay 141 is short-circuited over the test leads 201, 201<1> when connection is made to a second selector E<3>, but not when connection is made to a selector E<2> owing to the provision of a resistance 295. The insertion of a coin earths the line 12 through the polarized collecting-magnet P, thus unbalancing a differential relay 130 and causing the removal of the shunt around the contact 184 of the repeater line relay 135. Establishment of privileged connection over path C, D, E<1>, E<2>, O (no coin required). A calling line is connected through the line switch C to a repeater D and first selector E<1>. The repeater line relay 135, energized over the calling line through a differential relay 130, closes the circuit of a release relay 136 which (1) earths the test lead 50 through a low-resistance retardation coil 138, (2) closes the polarizing circuits of relays 128, 132, and (3) energizes the relay 141 which opens at contact 196 the shunt around the impulse contact 184 of the line relay 135. The relay 135 also closes at contact 184 a bridge across the trunk 200, 202 including the upper windings of relays 128, 132 and the lower winding of a relay 133. The relays 225, 226 at the selector E<1> energize, the test lead 201 being earthed through a resistance 240, which is in shunt to the relay 141 so that the latter remains energized. At the first selecting-impulse, a relay 137, Fig. 2, (1) energizes a self-locking relay 128 which short-circuits the differential relay 130, and (2) at contact 190 closes a direct bridge across trunk 200, 202, thus improving the impulsing circuits. The selector E<1> operates in the usual way to find an idle second selector E<2> having access to a record operator O, the test leads 268, 201 being earthed through resistance 295. The second selector operates in the usual way, to select an idle circuit O, thereby energizing relays 320, 321 and lighting a lamp L<6>. On inserting a plug and depressing a key K, the operator receives a tone signal from the transformer T, Fig. 1, over the test leads 50, 201, 268 indicating the class of service to which the subscriber is entitled. The desired connection is then established and the connection released in the usual way when the subscriber hangs up. Prevention of non-privileged connection if coin is not inserted. If connection is extended to selector E<3> in an attempt to make an ordinary call, the test circuit 201 is directly earthed at armature 275 (no resistance such as 240, 295 being prov ded), so that the relay 141 is shortcircuited and completes a shunt circuit around contact 184 of the line relay 135, thereby rendering the repeater ineffective to extend the connection further. Establishment of ordinary connection with insertion of coin. If, however, a coin has been inserted before commencing the call, the line wire 12 is earthed through the coin-collecting magnet P, thereby unbalancing the differential relay 130 in the circuit of the repeater line relay 135. The relay 130 energizes a self-locking relay 134 which opens at 180 the shunt around the impulse contact 184 so that the selector E<3> &c. can be operated to complete the connection. As previously explained, at the first selecting-impulse, the selflocking relay 129 short-circuits the differential relay 130, so that the coin must be inserted before dialling the first digit. When the called subscriber replies, the back-bridge relay 400 reverses the current in the trunk 200, 202, thereby energizing the polarized relays 128, 132. The relay 128 locks up and extends the calling line direct to the connector, disconnecting all repeater bridges. Metering; collection or refund of coin; supervisory arrangements. On the response of the called subscriber, relay 128 energizes the meter 28 to check the collection of coins. When the calling subscriber hangs up his receiver, the selector E<1>, E<3>, H are released as usual, and relays 128, 132 in the repeater de-energized. Relay 128 opens the circuit of a relay 127, and during its release a slow relay 125 is energized to connect the coin-collecting battery B<2> over wire 105, armatures 155, 177, relay 140, leads 51, 12 to the polarized coin-collecting magnet P, which collects the coin. If the called subscriber does not reply, relays 128, 132 and therefore the relay 127 are not energized, and when the calling subscriber replaces his receiver, the slow relay 125 is energized over the contacts of relays 136, 137 and connects the coin-returning battery B<1> over wire 106 and the back contact of armature 155 to relay 140, leads 51, 12 and magnet P, which returns the coin. In each case, the relay 140 energizes a relay 126 which connects an interrupter I to a relay 133, which repeatedly interrupts the circuit of battery B<1> or B<2> to prevent sticking of the armature of the magnet P. The relay 126 also lights a lamp L<5> individual to the repeater, and energizes relay 125 which by closing a circuit over wire 107 brings into action the several relays and delay switch S shown in Fig. 2<A> to give supervisory signals if the magnet P fails to act or if either of the batteries B<1>, B<2> is out of order. When the coin is collected or returned, the earth connection is broken at the substation and the relay 140 and associated supervisory arrangements are restored. The relay 132 is provided in case the called subscriber should replace his receiver first, thereby causing the back-bridge relay 400 to restore the normal direction of current in the calling line. When this occurs, the relay 132 is de-energized and causes a relay 131 to again reverse the connection of the trunk 200, 202 with the calling line, so that the connection of the line 12 to earth through magnet P does not interfere with the de-energization of the connector line relay 401 when the calling subscriber hangs up. Specification 180,331 is referred to.