The 18A-04 is a multi-function relay switch controller manufactured by the Aeroflex Company. It is mainly used in applications requiring high speed switching of multiple relays, such as in broadcast and military communications. This controller has sixteen relay outputs, each of which can be configured for either momentary or latching function. It also features an additional solid state output for driving opto-isolated LEDs and other auxiliary indicators. Additionally, it offers four programmable operating modes and is designed to operate on a variety of power supplies (5v, 12v, 24v, and 48v). It is available in both a standard and an expanded version, the latter providing additional features such as increased relay capacity, adjustable time delays, and alarm signaling.