Patent GB-228828-A (GB)
Title: Automatic switching arrangements for reversing the direction of traffic over a telegraph line or cable
IPC: H04L5/18
Filed: 1923-08-02
Abstract: 228,828. Western Electric Co., Ltd., (Western Electric Co., Inc.). Aug. 2, 1923. Automatic telegraphs; distributor systems; type-printing telegraphs; synchronous movememts.-In a telegraph system provided with a transmitter and a receiver at each end of a line, traffic in opposite directions over the line is controlled by the provision at each station of a switch for connecting a transmitting distributor and a receiving distributor at that station alternately to the line, and a timing-device for controlling the period of such connections, the distributors co-operating with the switches to connect the transmitter at one station and the receiver at the other station to line a plurality of times during each period. Multiple-channel distributors may be used. Each distributor is provided with a transmitting face 130, a receiving face 131, and a correcting face 132 over which travel brushes 133, 134, 135 respectively carried by the shaft 154 of an impulse motor 136 driven from a fork 137, and synchronism of the shafts 154 is maintained by impulses at the receiving station passing through a leak relay 138 associated with a corrector relay 139 for short-circuiting a resistance 140 in series with the magnet 141 driving the fork. The timing-devices are driven from a shaft 152 rotated at one revolution per minute through gearing 155, 156 from shaft 154, a cam 153 on shaft 152 closing contacts at 164 once in each revolution. A shaft 157 carrying cams 158, 159, and 160 is driven from the shaft 152 through a reduction gearing of one in twenty. These cams are formed with projections and depressions arranged to operate followers 161, 169 and 170 respectively at intervals equal to the desired durations of traffic in opposite directions over the line, and such operation is arranged to occur when the contacts at 164 are closed. A switch 166 is positioned to close a circuit controlled by the follower of that cam which it is desired shall be operative for this purpose. The projections and depressions operate the corresponding follower to close a circuit from - battery 165 and from + battery 168 respectively through the switch 166, contacts 164, and a conductor 167 to segments 171, 172 on the distributor faces 130, 131 respectively. With the station arranged for transmitting as shown, the line is connected to the continuous ring 186 on the transmitting face 130 through a condenser 185, a conductor 184, and an armature 183 of a relay 182. The brush 133 after traversing the transmitting segments 143 connects segment 171 to a segment 173, which is connected to ground 178 through a polarized relay 174 and an armature 176 of a relay 177. If, at this moment, the cam follower is in operative position, an impulse passes through the relay 174 in a. direction to reverse its armature, thus energizing relay 182 and moving the armature 183 to disconnect the line from conductor 184 and connect it through a conductor 191 and a shaping network 190 to the receiving relay 146 controlling the pointer relay 147 and the leak relay 138. A second atmature 188 connects ground at 187 to a conductor 181 to close a circuit through the still closed contacts of the timing device and through a polarized relay 180 at the next passage of the brush 134 over segments 172 and 179. This impulse reverses the armature of relay 180, thus energizing relay 177. One armature 193 of this relay closes a contact to connect the continuous ring 192 on the receiving face 131 to the armature circuit of the relay 147. The second armature 176 opens the circuit of the relay 174 and connects the pointer magnets to ground at 178. A third armature 198 removes ground at 196 from resistance 140, thus placing the speed correction of the fork 137 under the control of relay 139. The station thus becomes the receiving station and so remains until the cam follower of the timing device again becomes operative, whereupon a similar sequence of operations makes it the transmitting station again. Means are provided for ensuring that the cams of the timing-devices at the two stations shall close the corresponding contacts simultaneously. For this purpose a friction drive 200 is provided between the shafts 154 and 152, and an arm 201 on the shaft 152 is engaged by a detent 203 held against spring action in engaging position by an electromagnet 202 controlled by a polarized relay 204 connected to line through an inductance 208. This inductance prevents operation of the relay 204 by currents of signalling frequencies. The distributors at the two stations harving been brought into isochronism and correct phase relation in known manner, either of two selector keys 205, one at each station, is operated to send a negative impulse to line, thus causing the relays 204 to open the circuits of both magnets 202 to start the shafts 152 in correct phase relation. A second selector key 206 at each station enables a positive impulse to be sent to line to stop the shafts 152 preparatory to starting them in correct phase relation.