Abstract: A test control circuitry conducts an electrical current through a thermo electric cooler for the purpose of testing the operability of a thermal control unit. At temperatures higher than a temperature threshold, this electrical current is directed such that the thermo electric cooler cools a temperature sensitive switch. The direction of the electrical current is inverted at temperatures lower than such temperature, causing heat to flow to the temperature sensitive switch. These specified temperatures of the test control circuitry are programmable either manually or automatically from a remote computer linked to the control circuitry. Optionally, a temperature sensor such as a thermocouple or thermistor and their associated electrical circuitry is used as temperature sensitive switch. In such cases its temperature threshold is programmable.

Abstract: Pressure control device, characterized in that it comprises, in combination with valve means having an open and a closed position and urged to said closed position by a pressure thrust, elastic means opposing the closure of said valve means by exerting thereon an elastic counterthrust opposed to said pressure thrust, said means being normally in a condition of normal strain or stress wherein it creates a first level of elastic counterthrust such as to be overcome by said pressure thrust when it exceeds a first predetermined level; and means for bringing said elastic means to at least another condition of strain or stress, wherein it creates a second level of elastic counterthrust such as to be overcome by said pressure thrust when it exceeds a second predetermined level.