The FOI-2191 and FOI-2911 both provide complete electrical isolation for RS-232 communications. For compatibility with MIL-STD-188C, the transmit and receive data (TD and RD) can be inverted through either unit by a switch. The units are transparent to all handshaking protocols and can accept data and clock signals up to a maximum rate of 128 kbps. A regeneration switch on the FOI-2191 allows users to toggle between synchronous applications that require Send Timing (ST) and asynchronous or synchronous applications that require Terminal Timing (TT).