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Here are several closeup pictures of the DIY 8-line telephone system. 

Closeup of 8 line DIY automatic telephone system

Views of the rear side

Distribution panel 8 lines DIY phone system

Jacks for eight phones

Dial tone generator for DIY automatic telephone system

                               Dial tone generator

                         From an “Army Surplus” store

Closeup of line and CO relays for 8 line DIY automatic telephone system

Closeup of the Line (upper) and CO (lower) relays for phone #2


The dust covers kept the relays in pristine condition even after ~50 years of storage and a destructive water leak.

The majority of the relays were manufactured by C.P. Clare & Co., while the four rotary steppers were produced by the Automatic Electric Company. Notably, no parts were sourced from AT&T as they did not cater to public sales. Due to iterative design, seven additional relays were incorporated beyond the initial plan of approximately 46. As a result, supplementary relays were discreetly positioned on the inner side wall.

four Supplemental relays for STEm DIY 8-line phone system

Four supplemental relays mounted rear, inside wall

DIY STEM 8-line phone system power supplies

Selector usage monitor lamps, AC voltage adjuster, transformers

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