Patent GB-247711-A (GB)
Title: Improvements in or relating to automatic or semi-automatic telephone systems
IPC: H04Q3/00
Filed: 1924-12-31
Abstract: 247,711. Coventry Automatic Telephones, Ltd., and Collyer, J. E. Dec. 31,1924. Automatic exchange systems.-A connector, in which two slow-release relays energized during the rotary motion are de-energized successively when the wanted line is reached and in which the test wiper, disconnected during the rotary motion, is connected upon the release of the first relay to the test or busy relay and upon the release of the second relay to the switching relay, is adapted for private branch exchange working, hunting taking place only when the first line of a P.B.X. group is dialled. The change-over relay is adapted to serve as a stepping relay for effecting the automatic hunting, whilst the last or busy relay serves also as the ring-cut-off relay. Figs. 2' and 3 show two circuit arrangements according to the invention, whilst Fig. 1 shows the operation of an ordinary connector, not in itself forming part of the invention, from which the cricuits in Figs. 2 and 3 are developed. Ordinary connector, Fig. 1. The line relay 1 energizing over the conductors 11, 12 in series with a resistance 8 operates relay 2 and the latter closes a circuit for relay 3. The tens impulses are repeated over contacts 13, 20, 18, 22 to the vertical magnet 23 and at the end of the digit, relay 3 which remained locked up during impulsing over contacts 25, 24, 17, 16 de-energizes. The first units impulse is thus repeated to the rotary magnet 26 and relay 4 in parallel, subsequent impulses passing over front contacts 18, 22" owing to the operation of relay 4 which also completes a circuit 16, 17, 28 for relay 3. Busy test. At the end of the units digit, relay 4 de-energizes and disconnects relay 3 and during the interval before relay 3 releases the test wiper 29 is connected to the test relay 5 over contacts 31, 30. If the wanted line is busy, relay 5 operates and locks up and upon the release of relay 3 a busy tone and lamp-flash signal is transmitted over the circuit 34, 36, 37, 8, 11. Ringing. If the wanted line is idle, relay 5 does not operate but upon the release of relay 3 the switching relay 6 operates over the test wiper 39, locks up by removing a short-circuit from its lower winding, and connects up the ringing lead 39 over the lower winding of the test relay 5, a condenser 46 permitting a ring-back signal to the calling subscriber. When the called subscriber replies, relav 5 operates to disconnect the ringing current and completes the circuit of back-bridge relay 7. Release; signalling delay of calling subscriber in hanging up. When the called subscriber hangs up, relay 7 releases and completes a. circuit 16, 17, 32, 49, 50 for lamp 48 in an ,alarm circuit 51. When the calling subscriber hangs up, relays 1, 2 release and, the release magnet 53 operates. Rotary connector, Fig. 2. The operation in response to the tens and units digits is similar to that described above. The first line of a P.B.X. group has its fourth terminal 160 earthed through a resistance and the remaining lines except the last have the fourth terminals strapped to the ordinary test terminals. If therefore the first line of the group is called and is busy, the release of relay 104 completes a circuit for the test relay 105 over the test wiper 129, and relay 105 completes a circuit 116. 117, 162, 125, 161, 164 for relay 108 which locks up and connects relay 103 in series with the upper winding of relay 104 to the fourth wiper 158. Relays 103, 104 being energized in this circuit, release relay 105 and complete a circuit 116, 117, 128, 166, 120, 118, 122 for the rotary magnet 126 which advances the wipers one step and disconnects relay 103. The latter releases and opens the circuit of magnet 126. If the next line is busy, relay 103 operates again over the earth on the strapped fourth terminal and stepping thus goes on until an idle line, or the last line is reached. when relay 103 does not operate again. If an idle line is reached. the release of relay 108 following the release of relay 104 connects the test wiper 129 to the switching relay 106. If the last line is busy, no circuit is completed for relays 103, 104 and relay 105 operates and connects up the busy signal. If a line other than the first or last of the group is called and is found busy, relay 108 is shortcircuited over the earth on the strapped fourth terminal and no stepping circuit is completed. If the last line is called and is busy, relay 108 operates but no circuit is closed for relays 103, 104. Modified rotary connector, Fig. 3. In this arrangement, the first line only of a P.B.X. group has its third and fourth terminals strapped, the last line has its fourth terminal connected to battery and the intermediate lines have the fourth terminals disconnected. If the first line is called and found busy, upon the release of relay 204, relay 208 energizes over the earthed fourth terminal 260, closes a locking circuit 270, 271, 217, 216, and operates relay 204 over contacts 256, 262, 217, 216. Relay 203, before releasing, completes a circuit 216, 262, 256 for the rotary magnet 226. Relay 204 connects relay 203 over interrupter contacts 255 to the test wiper 229 so that if the next line is busy, relay 203 again operates and energizes the rotary magnet 226. The wipers are thus stepped round until an idle line is reached, when relay 203 no longer energizes, or until the last line is reachd, when relav 208 is short-circuit over the low-resistance 273 and releases. If the last line is busy, the test relay 205 energizes in series with relay 208 which does not operate and a, busy signal is transmitted over the circuit 234, 276, 274, 201. If a busy intermediate line is called, no circuit is completed for relay 208 over wiper 258 and automatic hunting does not take place.