The 1700M Series from DGH Corp., Manchester, NH, enables computer monitoring and device control through solid-state relays or TTL signals, sending digital I/O status to the host via Modbus RTU over RS-232 or RS-485. You can set the input or output direction of each digital bit individually or all at once. The series includes the D1711M/D1712 15-channel digital I/O module with RS-232/RS-485 and the H1750M and H1770 24- and 64-channel digital I/O boards with both RS-232 and RS-485. You can string up to 247 boards/modules over 1 twisted pair using RS-485. You can store initial digital output value and user-selectable options in EEPROM.