USB Relay Terms and Usage Page

Relays on the J-Works USB relay module are electrically controlled when commands sent from a host PC over the USB. Software API's (Application Programming Interface) provide users to write applications to control the relays from popular programming languages
The relays themselves consists of a coil of wire wrapped around a iron core, a yoke which provides a low reluctance path for the magnetic flux generated when the power is applied across the core. This then moves a amature connected to one or more sets of contacts.

(SPDT) Single Pole Double Throw USB Relay

A SPDT relay has one set of contacts the connects a common terminal to a normally closed contact when not on, and a normally open contact when on. This allows the routing of a signal to either of the output terminals

(SPST) Single Pole Single Throw USB Relay

(DPDT) Double Pole Double Throw USB Relay