Railway wheel counter and block control systems

A railway vehicle detector for sensing a passing railway vehicle wheel travelling along an elongated rail connectable to a processing means, said detector comprising:

• a. means for supplying an alternating current having a preselected frequency;
• b. at least one wheel sensing element, including a resonant tank circuit having a resonant frequency, excitable by said alternating current, said tank circuit being arranged for producing a voltage change as said wheel is travelling adjacent said at least one wheel sensing element due to a change in the effective inductance in said tank circuit as the wheel passes;
• c. the at least one wheel sensing element being connectable to the processing means for receiving said voltage change and responsively producing an output signal indicative of the presence of said wheel,
• wherein said preselected frequency is proportional to the resonant frequency of the tank circuit, and further wherein said preselected frequency is the frequency required to operate the tank circuit at a voltage approximately equal to a range between one half of the voltage across the tank circuit when operated at the circuit's resonant frequency and the voltage across the tank circuit when operated at the circuit's resonant frequency.