The Model 7050-C is a combination Rate-of-Rise and Fixed Temperature detector. A set of normally closed contacts will open when the surrounding air temperature increases at a (minimum) rate of 4 Celsius degrees (6 degrees F.) per minute. Opening the contacts initiates the alarm sequence. Independent of the rate-of-rise operation, the fixed temperature portion consists of a spring-loaded plunger retained by a fusible alloy that releases when the ceiling temperature reaches 57 degrees Celsius, (135 degrees F). When released, the plunger strikes the contacts and holds them open.

The Model 7050-C is installed on brackets on the door inside the vault, with the heat collector facing toward the door. It is important that the brackets are arranged so that they will not interfere with convection currents that may pass by the detector. The unit may be vestibule mounted as well providing that it is as close as possible to the vault door in the closed position.