Patent GB-244587-A (GB)
Title: Improvements in automatic or semi-automatic telephone systems
IPC: H04Q3/00
Filed: 1924-12-29
Abstract: 244,587. Western Electric Co., Ltd., (Western Electric Co., Inc.). Dec. 29, 1924. Automatic exchange systems.-Call-finders of the no-normal type, each having access to a number of groups of subscribers' lines, have a starting circuit associated with each group, these circuits being so controlled that only those idle finders which have their brushes resting within the group containing the calling line are set into operation. If there happens to be no idle finder within the calling group the starting circuit is extended to start idle finders which are resting within the next group. In the system illustrated, the finders 104 - - 106 are panel switches the brushes of which move alternately upwards to the top of the panel and downwards to the bottom. Commutator strips 122, 123, 162, &c., of which there is one in each finder for each group of calling lines, are engaged by extra brushes 125, &c. to control the starting circuits. Alternately the strips 122 &c. and brushes 125 &c. may be replaced by multipled terminals engaged by a fifth brush which is arranged adjacent to the other brushes but is constructed to bridge from one terminal to the next. In the Figure, finders 104, 105 are shown resting in group 1 and finder 106 in group 2. Operation when there is at least one idle finder resting within the calling group. It will be assumed that finder 104 is busy in a call made by subscriber 101, when another call is initiated by subscriber 102. Line relay 117 connects battery through resistance 119 to the multipled fourth terminal 147 and connects ground to operate the group relay 120. Relay 120 connects ground over relay 121 to strips 122, 123, 124 but a circuit is only completed over strip 123 (relay 111 being energized in the busy finder 104). Relay 128 operating over strip 123 closes a circuit for the up-drive magnet 130 which raises the brushes to the top of the bank when relay 131 operating over brush 138 tilts the freely-mounted armature 142 and switches over to the down-drive magnet 140. The brushes are then driven downward over the terminals of group 1 until the calling line 102 is reached when relays 132, 148 operate over brush 134 and resistance 119, the former disconnecting the driving circuit and the latter short-circuiting its high-resistance winding to prevent seizure by another finder. Relay 132 also completes a circuit for the cut-off relay 118 in series with switching relay 149 which remains locked up to ground 150 throughout the connection. Relay 149 energizes relay 127 which disconnects both driving magnets and also disconnects the starting relay 128 from brush 126. Operation when there is no idle finder resting within the calling group. Suppose now that with finders 104. 105 busy as above, a call is made by subscriber 103 in group 4. The operation of group relay 156 is unable to complete a circuit over relay 157 so that relay 120 operates over the back contact of relay 157. Relay 120 is similarly unable to complete a starting circuit over relay 121 so that relay 133 is operated and closes a circuit over relay 161, strip 164, brush 129 and relay 166 of the idle finder 106. The brushes of this finder are driven downwards over group 2 until brush 129 leaves strip 164. A new circuit is then completed for relay 166 over strip 169 and relay 171, relay 170 being operated over the back contact of relav 161. The brushes continue to move downwards in a similar manner over group 3 and into group 4 where a circuit is completed for relay 166 over strip 160 and relay 157. When the calling line 103 is reached, relays 174, 168, 178, 165 and the cut-off relay 175 energize as before.