The ACS104A is a complete controller, driver and receiver IC, supporting fullduplex asynchronous transmission from DC to 162kbps over a serial link. Improved sensitivity and additional operating modes are offered over the ACS104. Although primarily designed to be used with standard LED emitters and PIN receivers and twin optical fibers, any other simple serial media may be used. The ACS104A is optimised for very low power consumption, consuming only 2 3mA at RS-232 data rates including power provided to the LED and 'heartbeat' monitor. In applications where the power is extracted from the RS232 data lines, this leaves a generous amount of power left for any power extraction and RS-232 level shifting circuitry.