Portable bridge and insulation test set, a multi-function electrical testing instrument used for measuring resistance, insulation and circuit continuity in field and workshop environments. Housed in a rugged metal case with twin analogue meters, decade controls and test terminals, it allowed engineers to diagnose faults and assess wiring and equipment condition.
Such units were widely used by electrical utilities, telecommunications engineers and maintenance departments prior to compact digital testers and automated diagnostic instruments; mid-20th century, circa 1950s–1960s.
