How to Install Electric Bells, Annunciators, and Alarms. / Including Batteries, Wires and Wiring, Circuits, Pushes, Bells, Burglar Alarms, High and Low Water Alarms, Fire Alarms, Thermostats, Annunciators, and the Location and Remedying of Troubles

by Norman H. Schneider

Bell-ringing Transformers.

The best system for operating bells and annunciators from alternating current circuits is undoubtedly that employing small specially constructed transformers to reduce the voltage. These transformers are being used universally for hotel and office work where alternating current is available. They are simple, being merely one or more coils of well insulated wire wound on soft iron cores and having connections for both the lighting circuit and the bell circuit.

As a general rule the coils are divided as to their number of turns or according to the ratio of transformation desired. For example, if the circuit were 110 volts and 10 volts was required for the bell circuit, the total number of turns in the transformer would be connected, 10/11 to the lighting circuit and 1/11 to the bell circuit.

The bell-ringing transformers on the market are made in several styles. One small style, [Fig. 64], for single residences, is for use on 110 volts and produces a bell voltage or secondary voltage as it is termed, of 6 volts. Another size, [Fig. 65], of this transformer has three secondary voltages 6, 12 and 18, each of which can be used by connecting to the right binding posts.

Fig. 64

Fig. 65

BELL-RINGING TRANSFORMERS.

It is to be noted that where the lighting service voltage or primary voltage varies from the above, the secondary voltage delivered to the bell circuit will vary in like proportion. It should also be noted that a careless reversing of the connections, that is connecting the secondary leads to the lighting circuits, instead of the primary leads would cause a like high voltage at the other terminals of the transformer, raising it in due proportion instead of lowering it. Thus such carelessness would produce a voltage of 2,400 volts instead of 6 if a transformer intended to deliver 6 volts from a 120-volt circuit was wrongly connected.

The results might very well then be dangerous. All transformers are properly marked, however, and such an error only occurs through ignorance or carelessness.

The installation of these bell-ringing transformers is simplicity itself; they require no care after installation and have met with the approval of the National Board of Fire Underwriters.