Telephone, and other wire, lines go bad and need to be repaired. In order to locate shorts and opens an impedance bridge can be used. The ZM-4 was designed for this purpose.
This may be the same as the Leeds & Northrup 5430-AM-1 Test Set.
This may be the same as the Beckman Long Line Telephone Test Set KS-14959 (See BSP 100-815-101).
This is very similar to the Shallcross Wheatstone Bridge 6101.
MIL-B-3667B, 3067BN1, 3067INA, 3067CAN - Mil specs for the production of the ZM-4Back to Brooke's Products for sale, Military Information, Home page
TM 11-2019 Manual covering the ZM-4A/U and ZM-4B/U also the I-49() Resistance Bridges 70 pages.
This is a comprehensive manual including a number of practical example cases. Includes the case where a telephone system has not just a simple home run pair, but a more realistic situation where there are bridges where the branches and main line use different gauges of wire.TM 11-6625-249-12P Repair Parts 14 pages
Also has a theory section describing the different types of bridges.
TM 11-6625-249-34P Repair parts & Tools 23 pages
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ZM-4 Manuals to U.S. mailing address $ 15.00
ZM-4 Manuals to international mailing address $ 20.00
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Page created 27 Sep 2003.