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The Evolution of the Thermal Switch From United Control to Honeywell

1949 - 1974: United Control Corporation

In 1949, three former Boeing Engineers formed United Control Corporation (UCC). Bimetallic controls were already in existence when UCC was created; however, the founders believed they could improve upon the designs and materials of the day. They took this concept to market and rapidly built the company. The original UCC facility was located in Seattle near the University of Washington campus.

UCC manufactured thermal switches for various aerospace applications, focussing initially on applications for Boeing and later for other manufacturers. These switches were originally used on the B47, B52, P3 Orion, every Boeing and Douglas commercial jet, Lockheed's L1011, and the F16, and many other military platforms including Hughes helicopters.

1974 - 1994: Sundstrand Data Control

A new facility was built in Redmond, Washington, in 1969; and in 1974, Sundstrand Data Control purchased it. In the late 70's the Union Pacific Railroad asked Sundstrand to design a "reliable" replacement locomotive temperature control switch. At the demand of Union Pacific, General Motor's Electromotive Division tested (1 million cycles) and certified Sundstrand's replacement switch for their locomotives. The switch is still available today as an aftermarket conversion. Because of its outstanding reliability it carried a 4-year warranty (3 ½ years longer than the closest competitor.

The space industry also required high quality, high reliability (hi-rel) thermal switches. UCC entered the space market by manufacturing switches for the Titan Missile programs. Switches for the Titan program were produced until the 1980s. These units became the predecessors of today's 500 Series Switches (TS500). UCC/Sundstrand switches were also used on the Apollo programs. After the Apollo 13 incident NASA moved to a five-time redundancy requirement. At that time, our Apollo involvement focussed on the Lunar Rover.

The Viking Lander application demanded the next step in product evolution. It inspired the birth of today's hi-rel switch. These switches had to last much longer than a multi-week lunar mission - they need to survive a 2-year trek to Mars and function after arrival. And they did!

Thermal switches also flew on the first spy satellites in the early 70s. Military and civilian space customers used these sensors through the years and in 1988 the 770 Series High Reliability thermal switch was designed for "Manned Space Flight". The 770 became the 700 Series (TS700) in 1998. For the same price, customers received a dramatic improvement in reliability. These units are guaranteed to last 100,000 cycles and operate beyond 1,000,000 cycles in low current applications. There has never been a confirmed operational failure of a TS700 switch.

AlliedSignal 1994 - 1999: AlliedSignal

In 1994, AlliedSignal purchased the Sundstrand campus along with its thermal products, accelerometer and avionics businesses.

1999 - Present: Honeywell
Honeywell AlliedSignal merged with Honeywell in 1999, keeping the globally recognized Honeywell name.

The next evolution of the thermal switch will likely incorporate an onboard temperature sensor. A number of hi-rel space customers, aerospace manufacturers and railroad customers are interested in a unit which can function as consistently as the half-century old, extremely reliable, mechanical thermal disk switch and yet also give real-time temp feedback at the switch location. Such a product is under development today and is patent pending.

Through numerous corporate and ownership changes the thermal switch technology and manufacturing processes evolved and improved. Today our employees continue to deliver the high level of quality, reliability and overall excellence that our customers have come to expect during the past 50 years.

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