GB225068A - Improvements relating to automatic and semi-automatic telephone systems - Google Patents

Abstract

225,068. Coventry Automatic Telephones, Ltd., and Collyer, J. E. Dec. 5,1923. Automatic exchange systems; metering. - Metering is effected over a fourth wiper of the line switch by a relay at the first selector which has already been employed in the setting up of the connection, and which is energized again by booster battery applied to the test wire at the connector. The invention is described with reference to a selector of the Strowger type in which metering is effected (1) by the change-over relay and (2) by the rotary stepping relay. The line switch may be of the type shown in Specification 208,075. Metering by the change-over relay, Fig. 2. Line relay 101 and release relay 102 energize in the usual manner, and change-over relay 103 operates over its lower winding and connects up relay 104. Relay 101 repeats the dialled impulses to vertical magnet 106 at back contact 118, and holds relay 103 when off-normal contacts 113 are operated at back contact 124. Relay 103 relapses when the impulses cease and connects up rotary magnet 107, while stepping relay 104 remains held over off normal contacts 113 and interrupter contacts 126. Rotary magnet 107 and stepping relay 104 interact as long as the test wiper engages earthed terminals to energize the latter. When an idle line is found, switching relay 105 which was previously short-circuited over the test wiper energizes and extends the talking and test wires. Relays 101, 102 release, and the upper winding of change-over relay 103 is connected to the test wire, to which booster battery is momentarily applied at the connector when the called subscriber replies. Relay 103 then operates and closes the metering circuit 117. When earth is removed from the test wire at release, relay 115 falls back and connects up release magnet 108. Metering by the rotary stepping relay, Fig. 3. Rotary stepping relay 204 operates over its upper winding in the setting up of the connection, and when switching relay 205 energizes, its lower winding is connected to the test wire, so that it responds to booster battery to close the metering circuit. Alternatively, the lower winding may be dispensed with, since switching relay 205 locks to the test wire at contact 228 in series with the upper winding of relay 204, which does not operate until booster battery is applied on account of the high resistance of the former.