The software supports USB Relay boards which use HID technology, specifically MagiDeal 5V USB Control Switch. Relay boards are available with either 1, 2, 4 or 8 relays and are sold under a variety of names (more information below).
Select a board by serial number, then set the relay state when in receive and transmit. To test the board you can change the current relay state:
If enabled, the board is opened when you start this program.
Vendor ID 16C0, Product ID 05DF. These are the recommended boards (below), the relay count and status can be read and is shown in the Current column.
Vendor ID 0519, Product ID 2018. These boards are also supported however the relay count and status cannot be read. The relay count is assumed to be 8, the status is shown as N/A in the Current column.
Be careful - not all USB relays are the same.
eBay: New 5V USB Relay 2 Channel Programmable Computer Control For Smart Home - name not always the same, but can be identified by: