Figure 9-13.--Ten-line alarm switchboard.

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Figure 9-13.--Ten-line alarm switchboard.

The equipment necessary for supervising a circuit

The B-51 alarm panel, or two-line alarm unit (fig. 9-

or contact maker is comprised of an alarm-target

14), provides complete equipment for supervising two

relay, a supervisory-target relay, and a three-position

circuits or contact-maker lines. Five of these alarm

rotary switch. Two sets of the equipment constitute a

units are mounted for each 10-line panel.

two-line alarm unit.

Each unit is secured to its case by four screws.

The two-line panel has two alarm relays mounted

This method of mounting permits the inspection of a

side by side at the rear and near the bottom of the unit

unit by simply removing the four screws and pulling

panel. Each relay has an indicator drum that projects

the unit out of its housing.

9-12