TO-3 at Motorola around 1955. The lead spacing was originally intended to allow plugging the device into a then-common tube socket. The metal package can be attached to a heat sink, making it suitable for devices dissipating several watts of heat. Thermal compound is used to improve heat transfer between the device case and the heat sink. Since the device case is one of the electrical connections, an insulator may be required to electrically isolate the component from the heatsink. Insulating washers may be made of mica or other materials with good thermal conductivity. The case is used with high-power and
Compression seal fitting or conductors from twisting and shearing. One or more insulators may also be included when electrical isolation is required. Soft sealant technology for compression seal fittings was developed in the 1950s by Conax Technologies. Since then, compression seal fittings have evolved to include multiple variations for different applications. Some applications include: Single-element compression seal fittings are used to seal a single element such as a temperature probe, tubewell, pipe, etc. Multiple-element compression seal fittings are used when multiple elements of the same or different diameters such as metal tubing, ceramic or rigid plastic tube or pipe, temperature probe, a tubewell,