This board lives in the HIRES CCD footlocker. The solid-state relay board was designed to be a general purpose board that can be used to switch 120VAC equipment on and off. It was designed to fit into a 3U board slot. The board contains three connectors; a 6-pin Molex power supply connector, a 3-pin Molex input connector and a 6-pin 0.156 style Molex output connector. The power supply connector brings +5v into the board and wires it to the +5V terminal on the 3-pin input connector. The reason for wiring it to the input connector is so that it can be used as the 'outside' supply for an optical isolator. Also, if the input signal will be used to supply the sink current to the relay, the +5V is applied to the + terminal of the relay by connecting a shorting block between W1:1 and W1:2. Again, for sinking the current a second shorting block is installed between W2:1 and W2:2.
To use the board in a current sourcing application shorting blocks are installed between W1:2 and W1:3 and W2:2 and W2:3. In this case, the optional pull-up resistor should not be used.