Improvements in telephone alarm call systems

摘要

577,258. Time alarm signals. MERCER, R. (Automatic Electric Laboratories, Inc.) May 11, 1944, No. 8360. [Class 118 (ii)] [Also in Group XXXIX] A telephone exchange is provided with apparatus for automatically ringing certain subscribers at pre-determined times of day. A common timecontrolled step-by-step switch G which makes one rotation in 24 hours and may for example rest for 7¢ minutes on each contact and also between adjacent contacts connects up in turn a series of relays D, each of which is common to the group of subscribers to be called at the corresponding time. Relays A, B, C are individual to each subscriber's line and a common relay E which energizes momentarily over cam F once per minute connects up relay B of each line associated with the operated relay D, provided the line is not busy. Relay B locks and applies ringing current to the line through ring-trip relay A which responds upon reply and lights lamp L1 individual to the subscriber. The ringing may be continuous or coded to distinguish the alarm call from an ordinary call. If the line is busy, relay C is operative and relay B is disconnected, and further tests are made when relay E energizes again. A pair of relays H, J which operate in succession over time-controlled cams K after relay D has energized and lock up as long as any relay A of the group remains unoperated serve to connect up an alarm bell AB and lamp AL a certain time after the calls are initiated, so that an attendant may check which lamps L1, L2 ... remain unlighted and take any necessary action. Relay D falls back when the switch G steps on and unlocks all relays A, B. In a modification, relay E and cam F are eliminated and a common group of lamps L1, L2 .... serves successively for the different groups of subscribers. Also, relay B is released by the operation of relay A so that the line is rendered free as soon as the alarm call is answered.