Supervision box with telephone
The supervision box is designed for connection to alarm board TL 300 and may be located, in the nearest police station. When a burglar-alarm contact has been actuated and this is indicated on the alarm board the bell of the supervision box will also ring. An additional supervision box TL 501 is mounted near the alarm board and
connected in series with the supervision box in the police station. A calling signal may thus be transmitted in both directions and conversations may take place between the supervision boxes over the supervision line. Case of black enamelled sheet-iron, relay for closed circuit control over the supervision, line to the alarm board, bell, switch for disconnecting the bell after an alarm, telephone instrument for communicating with the alarm board, press button for signalling to the alarm board.
The supervision box at the police station is connected to the alarm board by a two-wire circuit. When an overhead line is used, the branches are connected to the alarm box and supervision board over fuses ND 380/1.
Fault or injury on the supervision line is indicated at the supervision boxes. A battery composed of two dry cells RK 210 is required for each supervision box.
height 220 mm, width 215 mm, depth 95 mm, weight 3.2 kg.
Taken from the L. M. Ericsson Telephones and Signalling Material Catalogue No. 188 (1934)
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