The IntelliTools IT-R4S is a multi-purpose relay module allowing four internal single pole double throw relays to be controlled by an RS-232 port using a simple ASCII control protocol. Additional IT-R4S modules can be "daisy chained" to provide control of additional modules or other RS-232 devices. The IT-R4S passes RS-232 control data out to other RS-232 controlled devices via the unit's serial output port. Power Requirements: Power Supplies are sold separately. One Power Supply can power up to (6) IT-R4 and/or IT-R4S modules, saving wiring headaches and money.