Around 1921 Western Electric developed what would be known as the Double Button Carbon Microphone. The build and durability of these microphones would stand the test of time. Even today with the right equipment you can get them to work. The Western Electric 600A along with it’s earlier incarnation, the 387, are beasts. They are roughly 3 1/2 in diameter and about 2 inches deep. For it’s size it’s actually quite heavy being made from mostly nickel-plated cast iron.
The 600A was widely used in the broadcast industry, but realistically died off in the mid to late 30’s due to newer technology coming along.
The issue with Carbon Microphones is they require an external DC power supply (batteries), which most microphone setups today don’t supply. Normally you have 3 wires connected to the mic, 1 for power, 1 for ground and the 3rd to receive the signal.
When the Western Electric 600A came out around the mid 20’s, it was designed and built for the professional broadcaster. One famous event that used this mic was when U.S. President (Hoover) used it for his first inaugural speech.
The Western Electric 600As were often housed in the Western Electric 1-B desktop enclosures. These provided a little more protection from the elements and the occasional banging that might occur when using the mic.