This relay board will allow you to switch other electrical devices on and off.

Relay parameters :
The relays are Single Pole Double Throw (SPDT)
The relays can switch up to 240 VAC at 10 Amps and 100 VDC at 5 Amps.

Relay's datasheed :
RAS.pdf

Supply :
12 Volts DC
Minimum draws current - 100mA

Dimensions :
50 mm / 45 mm / 20 mm

Sample Arduino Code :

/*
  Relay control example
  Turns on an Relays on and off for half second, repeatedly.
 
  This example code is in the public domain.
*/

void setup() {
  // initialize the digital pin's as an output.
  pinMode(12, OUTPUT); // Relay 1
  pinMode(13, OUTPUT); // Relay 2
}

void loop() {
  digitalWrite(12, HIGH); // set the Relay 1 on
  delay(500); // wait for a half second
  digitalWrite(12, LOW);  // set the Relay 1 off
  delay(500); // wait for a half second
  digitalWrite(13, HIGH); // set the Relay 2 on
  delay(500); // wait for a half second
  digitalWrite(13, LOW);  // set the Relay 2 off
  delay(500); // wait for a half second
}