The Opto-22 G4IDC24 is a digital DC input module used to detect ON/OFF DC voltage levels. It provides up to 4000V (transient) of optical isolation between field inputs and the logic output of the circuit. It designed with filtering on the input and a hysteresis amplifier, providing high noise rejection and transient-free, 'clean' switching. Typical applications includes sensing the presence or absence of voltage and sensing contact closure from sources such as proximity switches, limit switches, selector switches, push buttons, photoelectric switches and TTL-compatible devices.