DPDT Relay Controller
This device has DPDT relays installed. A single DPDT relay is made up of 2 SPDT switches. Each relay acts as two switches that are activated at the same time. This allows two independent signals to be switched at one time. In effect, there are two independent switches on a single DPDT relay - they will always switch together.
There are two connectors with Normally Open, Normally Closed and Common for each relay allowing two separate connections. The picture above shows the 4-channel connectors. The diagram to the right shows the how the arms of the common connector swing from the Normally Closed to the Normally Open positions when energized. Wiring to either the NO or NC can produce your desired results. For more information on selecting the correct relay amperage for your application see Choosing a Proper Amperage.