A tube socket is an essential part of early electrical circuitry, especially in circuits required to create items such as working radios or the early television set. The tube, a glass tube similar to a light bulb, serves as a type of fuse or circuit completer. The tube acts as an indicator that the circuit through it has been completed.
Problems existed with these tubes, however, as they often burned out or were exhausted. They were also sensitive to sharp movements or dropping, such as a radio being knocked off a shelf. As a result, the designers of the circuit technology created a socket within the circuit to enable the easy removal and replacement of the tube. This allowed the user to have the tube, also known as a vacuum tube, properly tested for function or replaced in cases of tube failure.
When tube sockets were first designed, the chassis of most electronic devices was made out of some sort of sheet metal. The tube socket was typically bolted directly through the chassis, with the connection required to complete the circuit connected directly to the lugs or nuts on the underside of the chassis. When the tube was plugged into the socket, the connection was made with the contacts and the circuit was completed.
With the progression of circuit technology, tube sockets were manufactured to be directly implemented into the newer designed circuit boards. Typically, they were soldered directly into the contacts in order to complete the circuit. In order to correctly place the tube socket with the correct circuit contacts when the tube was inserted to complete the circuit, the pins of both the tube socket and the circuit contacts were numbered in a clockwise fashion.
After World War I, the advancements made in technology required expansive changes in the realm of electrical circuitry. These changes included the advancements of tube and tube socket design and technology. Whereas earlier tube sockets were basically manufacturer specific and thus widely non-interchangeable, newer circuit boards implemented tube sockets and tube designs that were interchangeable between brands and manufacturer. This resulted in shifts in design and size for manufacturers to remain competitive.
Tubes, along with tube sockets, became much smaller and more durable. They also become more easily replaced, as they were still prone to failure. Over time, as the technology changed, and the waves being used for radio and television evolved, the vacuum tube and the tube socket were adapted to remain current with each new technology that emerged.