What is IV HOG coupler or ZS coupler.

An IV coupler, or Inter-Vehicle Coupler, is a device that connects coaches in a train and transmits power between them. It's also known as a Coupler Unit.

Inter Vehicular Coupler Unit is used for EOG/HOG type coaches for transmission of 3 phase, 500 A, 5 wires, 750 V, 50 Hz power supply from power car to individual coaches.