DC Solid State Relay Board: This is a opto-Transistor with optical isolation between input signal and output signal. This is to be used for switching 24V-60VDC supply by 5V-230 VDC input signal. Features DIN rail mountable, compact and easy for troubleshooting. TwoFourEight phototransistors on a single board. Sink or Source type input connectable LED indication for input signal. Ideal to drive hydraulic and pneumatic solenoid coils. Built in free wheeling diode across driving load for every individual output point