T:  picture 1, top left

Red Phone Line Indicator Bulb


T:  picture 1, bottom left

V_AB(0) ≈ 50 volts :   free phone line
V_AB(1) ≲ 8 volts :   busy phone line


T:  picture 1, right

Deactivating time:   16 seconds  (t_från)
Activating time:   0.7 seconds  (t_till)


T:  picture 2, left

Power Supply

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