Patent GB-260330-A (GB)
Title: Improvements in or relating to telephone systems
IPC: H04Q3/00
Filed: 1925-07-20
Abstract: 260,330. Automatic Telephone Manufacturing Co., Ltd., and Passmore, W. O. July 20, 1925. Automatic exchange systems.-In a system in which the calling party is fed from the first selector, and in which the second and later digits are repeated over one speaking wire direct to the magnet of subsequent selectors, if the wanted line is busy, or if no free intermediate trunk can be found, ground is sent back over the same wire to initiate the transmission of a busy signal from the first selector, which at once releases the rest of the connection. A circuit is closed over the other speaking wire in the intervals between digits to initiate hunting in the second selector. Ringing current is supplied from the connector, and when the wanted subscriber replies the first selector detects the closure of his loop and meters the call. If the first or a later selector is set to a level of inter-exchange trunks the first selector modifies its circuits so as to repeat subsequent digits in loop form, and a polarized relay is brought into the loop to detect the subscriber's reply. First and second selectors. The vertical and rotary magnets V, R are operated in the ordinary way and when an idle second selector is found the relay H is energized. Ground on the wire RT' partially energizes a two-step relay H<1> to open contact 53. The second digit is repeated to magnet V<1> (over 1, 5, C, 14, 39, 15, 41, 57) and at its termination a circuit (17, G, 9, 36, 6, NR', 56, 52, N<2>) is closed to energize relay E<1>, which locks and energizes magnet R<1>. Relay E<1> is unlocked by R<1> and its original circuit is opened by a rotary off-normal switch at NR', but if the first trunk is busy it is energized again over the wiper p<2> and hunting proceeds as usual, the relay H<1> becoming fully energized over its lower winding when an idle trunk is found. Connector. Ground on the wire RT<2> energizes relay X. The third digit is repeated as before over the b wire to magnet V<2> and the fourth digit to magnet R<2>, in series in both cases with relay C', vertical and rotary off-normal switches N<4>, N<5> and NR<2>, NR<3> being operated at the first steps. Busy release and signal. If the wanted line is busy, relay BR is energized (over 74, 62, 73, p') and remains energized a moment after its circuit is opened by the relapse of relay C<1>, so as to ground the b wire (over 61. 64, 68, 78) to energize relay F in the first selector (over 41, 15, 10, 43), which locks itself, takes ground off the wiper p to release the subsequent switches, and connects the incoming a wire to a tone and intermittent battery wire IB. Ringing and metering. If the wanted line is idle, relay H<2> is energized over p<3> and completes the ringing circuit through relay BR, which becomes energized to complete the talking circuit when the subscriber answers. Relays G and F in the first selector are energized over the called loop and jointly energize the reversing relay D, which disconnects F and locks itself in its place (over 33, 43, 10. 15) so that the called line is fed through relays G and D. Transferring control of release to operator; preventing metering. If the call is to a local operator it is arranged that only the relay G is energized from her cord. In this case the wiper p is grounded (over CS, 30, 38, 32, 31, 42) independently of the calling subscriber's release relay B and the release magnet circuit is opened at contact 35. Signalling and metering " all-trunks-busy." If 11th-step contacts CS, CS<1>, CS<2> are operated, a statistical meter is energized over wiper p and relay F is energized to connect up the busy signal wire IB. Contact CS<3> in the second selector energizes relay F over the b wire and the second selector is released. Calls to other exchanges. The terminals engaged by an auxiliary wiper p<1> of the first selector, or by a similar wiper in a later selector, are connected to ground in the case of outgoing trunks so as to energize a relay Q, which connects relay G across the trunk in series with a polarized relay P, and prepares a circuit 2, 18, 6 over which subsequent digits are repeated in loop form. Relay P is energized when the called party replies and energizes relay D. Busy flash current from a subsequent exchange intermittently de-energizes relay G which repeats the signal by connecting the incoming a-wire to a tone and continuous battery wire CB.