overall: 11 1/8 in x 7 in x 7 in; 28.2575 cm x 17.78 cm x 17.78 cm
Object Name:
Microphone
condenser microphone
Date made:
1931
Date made:
ca 1931
ca 1931
ca. 1931
Description:
RCA / NBC "velocity" ribbon-type radio broadcasting microphone, inscribed "NBC," on the base, with the numbers "31-4" and "405530A4;" attached cord. A narrow, corrugated ribbon of aluminum alloy (without diaphragm) is caused to vibrate in the field of a permanent magnet by sound frequencies in its field of response. A current is generated in the ribbon corresponding exactly to the frequency and amplitude of the original sound. Bi-directional response field 90 degrees front and back. Diamond shaped perforated bronze metal case with NBC plates on black base. Marks cast inside of base 91-A.
