Abstract: The control system operates vehicles over a right-of-way divided into a plurality of zones and selects the direction of traffic along the right-of-way. The presence of a vehicle is sensed when it enters the zone from either direction and the occupancy of the zone is registered. The occupancy registration is indicated by a magnetically actuated switch to operatively control restrictive aspects in accordance with selected number of zones behind the leading vehicle relative to the selected direction of traffic.

Abstract: There is disclosed a double rail track circuit for use within a railroad block or each cut section of a block. Adjacent cut sections, or blocks, are separated by insulated rail joints. A transmission line having terminals accessible at each joint is provided. The transmission line has impressed thereon a modulated carrier signal to provide a reference signal at the modulation frequency. The reference signal derived from the carrier is coupled to one end of each block, or cut section, in such a manner that the signals of adjacent blocks, or cut sections, are out of phase with respect to each other. A synchronous detector is coupled between the transmission line and the rails at the other end of the block, or cut section, to compare the phase of the signal at the other end, with the anticipated signal phase. Band-pass filters may be used between the rails and the synchronous detector and between the transmission line and the synchronous detector and which do not pass common frequencies.

Abstract: A four terminal varistor is shown as a device for providing fail-safe circuit protection under certain conditions. The failure of any lead connected to the four terminal varistor will shut down the protected load so that the load cannot operate under unsafe conditions. By its nature, a varistor can absorb voltage peaks and protect a load from high voltage and/or a current resulting from high voltage. One pair of leads from the varistor is connected to the power supply and the other pair of leads to the load. Thus, if any lead is broken, there will be no power to the load. A variation provides additional protection in the event the metal coating on the semiconductor, to which two of the leads are attached, becomes detached from the semiconductor. In case of such detachement, the electrical connection between the two leads is broken. For this purpose, the metalized coating on the semiconductor is divided into two separate areas, one for each lead.