This Aube RC840T-240 Electric Relay comes with a built-in 24V transformer and is ideal for commercial applications. 

Note: Device was never used; box was opened for pictures.

Features:

Direct replacement for any brand name relay

Built-in 24 V transformer for easy installation

Compatible with 24 V thermostats with 2-wire connections (R, W) or 3-wire connections (R, W, C)

Immediate relay activation provides improved temperature control and comfort

Epoxy-soundproofed relay ensures quiet operation

Low current consumption means multiple relays can be controlled by a single thermostat