One channel relay board used in isolation circuit. Are you controlling any high voltage appliance.? Then this one channel relay board can do your Job. I-labz provides this easy interfacing modules to control any isolated high voltage DC or AC appliance. The board has one relay of 12V rating. I-labz relay board has 3 connectors on the board. These connectors are +12V, GND & Input. The input pin is the control pin to switch the relay between NO & NC.
The relay board is compatible to use with 8051, AVR, PIC, Arduino and even for Raspberry Pi. Most of the projects induced controlling the 230v AC powered bulb, Fan etc. These devices can be controlled with simple TTL logic using the relay board. If these are multiple AC appliance, then two channel relay, Four channel relay or even 8 channel relay boards can also be used.