Patent ID: 8725325

Claim:
An apparatus for braking a fixed guideway vehicle, comprising: an emergency braking system that is configured to apply an emergency braking force that is capable of bringing the vehicle to a complete stop at least at a substantially predetermined rate and with a predetermined degree of safety; and control circuitry on the vehicle for generating a withhold signal, wherein the control circuitry is configured to generate the withhold signal unless a predetermined safe command is not correctly received from an external source over a predetermined amount of time, wherein the external source is external to the vehicle in which the control circuitry is located, wherein the control circuitry includes: logic that receives a signal from the external source and extracts a command therefrom, the logic further generating a periodic signal only if the extracted command matches the predetermined safe command, the periodic signal generated by the logic having one or both of a predetermined frequency and a predetermined duty cycle; and a device that generates the withhold signal only when the periodic signal generated by the logic has one or both of the predetermined frequency and the predetermined duty cycle for the predetermined amount of time, and wherein the emergency braking system is configured to apply the emergency braking force whenever the withhold signal is not generated.