Switchboards SB-53/FTC and SB-53A/FTC
a make contact of the line jack to com- plete the circuit to ground for the oper- ation of relay 2. A make contact of relay 2 completes the trunk loop through windings (8-7 and 6-5 in series) of the repeating .coil to signal the distant…
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Free 72-hour kit. A short checklist PDF for the first three days, if you want a next step after this manual.
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