4-channel conversion between 5 Vdc TTL/CMOS and RS232 DB9 female connector. TD, RD, RTS, CTS support. Powered by pin/signals: 7(RTS), 4 (DTR), 3(TD); lines can be high/low, but must be present to power the converter. Pin 5 is SG for both connectors. Use with microcontrollers or PLCs supporting TTL.