Model HT-737 (digital) and model HT-761 (analog) are multi-functional humidity transmitters. They measure relative humidity, temperature, dew point, and absolute humidity.
737: RS-232 or RS-485 output capability
737: programmable micro controller
761: linear 0 to 1 VDC or 0 to 10 VDC output of ambient relative humidity and temperature
761: digitally adjustable