The practical telephone handbook and guide to the telephonic exchange (1906)
Poole, Joseph · New York, Macmillan Co. · leaf 131
M ETA l COVE-R … Fig. 110a Scale h Fig. Ericsson Instrument Protector 1106 Figs. 110a and 1106 show the Ericsson form of instrumentprotector which is now extensively used. The heat coils hand fuses f are separate and the former are so arranged thatwhen the fusible metal melts the spring clips s s fly open…
Telephone
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