Traffic light control for emergency vehicles

Claim 1

Apparatus for control of traffic lights for passage of an emergency vehicle, comprising: (a) a conventional traffic light controller (TLC), (b) first means for removing power from said TLC to leads leading to all of the traffic lights under control of said TLC; during at least a first selected time interval; (c) second means for applying power to selected ones, but not all, of said leads leading to said traffic lights during at least part of said selected time interval; (d) a directional antenna and radio transmitter connected thereto mounted in an emergency vehicle so as to transmit radiation in the direction in which said vehicle is moving; (e) an omni-directional antenna and radio receiver means connected thereto mounted at an intersection, for receiving radiation from all directions; (f) said first and second means responsive to a signal received by said radio receiver means; and in which (g) said radiation transmitted to said receiver means includes at least three tons of different selected frequencies, which are operated as two groups, only one group of which operates at any selected time; one of said two groups comprising a first pair of tones being transmitted alternatey on an on/off cycling; the second group comprising a second pair of tones; of which at least one tone is different from both of said first pair of tones; said second pair being transmitted simultaneously and continuously; and in which (h) said radio receiver means includes means responsive to both of said at least first pair of tones, and to their on/off cycling to control a timer means to close a selected electrical circuit through said timer means for a second selected time interval; and also includes means responsive to both said at least second pair of tones, and to their continuous nature, to by-pass said timer means, and to close said selected electrical circuit directly.