Electronics123.com, Inc. Serial Isolated I/O Module (Assembled & Tested) 8-Relay Module (mains rated - 110V and 250VAC.) 9-12V DC powered It is in a plastic case, latched relay operation, 250V relays switched in safety by using Dinkle connectors, and with 4 external inputs Uses serial port so it can be located over 100 yards from the PC Q: Can this module be used in standalone mode? A: No. It needs to be connected to a PC. However the state of the relays will be "remembered" and will not change when disconnected from the PC. Assembled and Tested