Left: BPO early model with porcelain mouthpiece . By Consolidated, from 1881. Photo courtesy Laurence Rudolf
Left: BPO early model with porcelain mouthpiece . By Consolidated, from 1881.
Photo courtesy Laurence Rudolf
Right: Internal view. Photo courtesy Ron Christianson, Cyber Telephone Museum http://www.museumphones.com/
Simpler turned wood mouthpiece, as used on the BPO phones.
Internal layout (note the large coil magnet for the receiver);
Final model with exposed transmitter diaphragm.
L to R: :
With longer backboard to accommodate magneto / bell box;
Japanese model with Ader-type receivers. A similar style was also used in some European countries.
British Post Office second pattern by Consolidated.
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