For use with the UC1 Universal Control, MAC1E or MAC4E auxiliary controls. The WHKE gas pressure switch actuates the Inducer /Venter through the A-B dry contacts on UC1, MAC1E or MAC4E. The Linear Limit switch disables the heater in the event of a venting malfunction. Includes JA1 thermocouple junction adapter. To interlock millivolt water heater(s) only with a UC1 controlled Inducer / Venter add a WHKE for each millivolt heater. To interlock a millivolt water heater and one 24/115 VAC furnace or boiler with a UC1 controlled Inducer / Venter, add a WHKE and a MAC1E. Tjernlund Millivolt Interlock Kit, Vertical Mount, Domestic