RCA 50-A (MI 4030-D)

From the 1936 RCA catalogue.

"The RCA Inductor Microphone is an outstanding result of RCA's continued development for a microphone having predetermined characteristics such as—freedom from shock excitation, minimum response to wind effects, high pick-up sensitivity and rugged compact construction, all of which are present in this unique instrument. Operation is achieved by means of a thin aluminium conductor rigidly coupled to a pressure-operated diaphragm. No excitation power is required. A self-contained transformer matches a 250-ohm or 50-ohm line."

From the 1936 RCA catalogue.

SPECIFICATIONS

Frequency Range: 60-10,000 Hz

Output level: -67 db. (10-bar signal-open circuit)

Output Impedances: 50 and 250 ohms

Fitting Size:½" pipe thread

Complete with 30 foot cable

A discussion of the RCA 50A and Western Electric 618 microphones at the Modesto Radio Museum.

A detailed post at the Coutant website about the RCA 50-A, including a link to the manual