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Application Converter M- 222 is designed to supply emergency power ringing current for telephone switchboards such as Switchboards BD-91-( ) and BD-96, when power from a 110-volt, 60 cycle source is not available or when the standard 110-volt power ringing equipment fails in service. Converter M- 222 is a component of Telephone Central Office Sets TC- 4 and TC-12.

Technical Characteristics

Power Source

Converter M-222 uses two 1 1/2-volt Batteries BA-23, connected in series, as a source of power. Battery life is approximately 8 to 10 hours under continuous operation.

Output Voltage and Frequency

The output of Converter M-222 is 100 volts alternating current open circuit, or 50 volts with a 5-watt load. The peak voltage will not exceed 250 volts. The frequency of the output voltage is 24 cycles ± 4 cycles.


Converter M-222 consists essentially of the following assemblies: Box. Converter M-222 is housed in a rectangular steel box with two removable sides. On the front panel are mounted an output receptacle, a nameplate, the lower section of one catch fastener, and Switch SW- 105. The switch is mounted in a recess in the panel. The ON and OFF positions of the switch are marked on the panel.

M-222 7.png


Related Files

Adobe PDF icon.png TM 11-344 (1943)

Technical Manual
March 16, 1943

Adobe PDF icon.png TM 11-344 (1946)

Technical Manual
April 1946