The Joint Efficiency Verification device is designed to detect insulation loss in the joints separating double-break TC sections.

The JEV consists of a Transmitter and a Receiver that exchange a signal at a frequency of 12 kHz or 18 kHz: the transmitter sends a Vtx signal to the ends of a joint, and the receiver detects it as Vrx from the ends of the corresponding joint on the opposite rail. If the joint is intact, the receiver generates a DC voltage Vout to energise a system relay. When one or both joints deteriorate, reducing the insulation resistance below a defined limit, the Vrx voltage drops beneath a certain threshold value and the Vout output supplying the relay is interrupted, causing it to de-energise.

The JEV is powered by an alternating voltage with a nominal value of 150Vac at 50 Hz. A diagnostic circuit provides an external RS485 serial port for connection and analysis of diagnostic data.