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Microphone Hummer (oscillator) 572-B

Microphone Hummer 572-B; General Radio (ID = 2258177) Equipment Microphone Hummer 572-B; General Radio (ID = 2258152) Equipment
Microphone Hummer 572-B; General Radio (ID = 2258166) Equipment
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Microphone Hummer 572-B; General Radio (ID = 2258177) Equipment
General Radio: Microphone Hummer 572-B [Equipment] ID = 2258177 933x650
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For model Microphone Hummer (oscillator) 572-B, General Radio Company; Cambridge (MA):
Underside showing part number 572-B and serial number 572-520
Country:  United States of America (USA)
Manufacturer / Brand:  General Radio Company; Cambridge (MA)
alternative name
Year: 1933 ?? Category: Service- or Lab Equipment
Main principle Audio-Amplification
Power type and voltage Direct Current supply (DC) / 6 Volt
Power out
from Model: Microphone Hummer 572-B - General Radio Company;
Material Metal case
Shape Chassis only or for «building in»
Dimensions (WHD) 79 x 42 x 50 mm / 3.1 x 1.7 x 2 inch

This microphone hummer is a 1KHz oscillator which is similar in principle to microphone driven tuning fork oscillators.  It works by mechanically coupling a carbon microphone to an electromagnetically driven vibrator bar, adjusted to resonate at 1KHz.  It appears in the Heathkit IB-1 and IB-1B impedance bridges and supplies an approximately sinusoidal, 1 KHz signal for AC impedance bridge measurements.  A carbon microphone serves as the active element which drives the vibrator electromagnet, and through a transfomer supplies the 1 KHz electrical output signal.  A 6 volt DC source powers the carbon microphone driven vibrator electromagnet.

The first and last years of manufacture of the 572-B are unknown, but the microammeter in the IB-1B has a manufacturing date stamped on the back: 22 November 1952.

The 572-B schematic appears in the IB-1 schematic in the Heathkit manual.

Mentioned in - - Manufacturers Literature (Heathkit IB-1 impedance bridge manual (circa 1949))
Literature/Schematics (1) - - Manufacturers Literature (schematic appears in the IB-1 manual)

Model page created by Gary Brandenburger. See "Data change" for further contributors.

All listed radios etc. from General Radio Company; Cambridge (MA)
Here you find 216 models, 197 with images and 84 with schematics for wireless sets etc. In French: TSF for Télégraphie sans fil.