The single-button carbon microphone was widely used in the "candlestick" telephone made by Western Electric, models 299 and 323, from 1915 to the 1920s. This type of microphone was suitable for the limited voice range of telephones, but carbon produced too much noise for music recording.
Hoover with radio mics
from Literary Digest 1929/05/04
The spring-mounted double-button carbon microphone was designed to keep the carbon granules inside the transmitter from moving and touching the diaphragm during operation.
1925 WE 1B used by Hoover
from Literary Digest 1925/12/19
373-W in the WE 1B mount
#25603 from AT&T Archives
The Western Electric 1A or 1B housings enclosed the same carbon transmitters used in the spring-mounted versions. The spring-mounted and enclosed versions were widely used in radio broadcasting 1921-1931.