Radio Signaling System for the New York Police Department

By means of the radio signaling system described it is possible, through the addition of a comparatively simple attachment to a standard radio telephone transmitter, to modulate the carrier with an audio frequency tone in such a manner as to provide for calling individually, simultaneously, or in a number of designated groups, any one of several hundred radio receiving stations. At the radio receiving stations apparatus is provided which may be operated from commercial sources of power supply and by means of which a visible or audible signal is given to the operator that a message is about to be broadcast, to which he should listen. Signals are also provided which, in case of improper operation, immediately inform the operator of the points at which attention is required.