221-2/3 High Temperature

The 221-2 and 221-3 are similar to the 121-2 and 121-3 but are designed to interface with fire alarm control panels, PLC's, etc.

The 221 requires 24 VDC and provides an open collector control for powering various devices.

The 221 offers a standard 4 wire interface with normally open, dry contacts.
The 221-2 has two fiber optic probes and the 221-3 has three.