What is an interposing relay?

An interposing relay is defined as a relay that isolates the driving circuit, switching a higher voltage or current than the circuit driving it can provide, according to SeaLevel.com. A relay device closes or opens a circuit under the control of an isolated and separate circuit.

Mechanical relays utilize a coil to start mechanical contacts, while a solid state closes and opens circuit paths by utilizing electronic devices, such as transistors, triacs and optocouplers to function like a mechanical relay. Another example is a reed relay, which has two magnetic contacts enclosed in a glass envelope, and an energized coil near the envelope creates a low-resistance connection by moving the contacts.