Leeds & Northrup Wheatstone Bridge Type S Test Set No. 5300

This is a gorgeous megohm meter built by Leeds & Northrup for Ma Bell (the Bell System) and Western Union Telegraph. This is a Wheatstone bridge with ability to perform Varley and Murray loop tests. Designed for finding fault locations on telecommunication lines. It is a portable device in a gorgeous oak case, and utilizes precision wire wound resistors via rotary switches, and a galvanometer. It is powered by batteries (3 x "D" cells) or can be connected to an external supply. The battery case is clean with no corrosion.

It can be configured to be a highly accurate resistance and its functionality is adaptable via knife switches. It has an internal, and an external galvanometer can also be connected. Instructions for usage and circuit diagram are glued to the inside of the lid. This bridge was first manufactured in 1915 and continued for several decades.  

This tester was the "go-to" tester for linemen in the day, for everything from determining the distance to a fault to counting the number of phones hooked up in a house. It also measured ohms and megohms (1 million ohms). Worked by using the capacitance of the wire pair to determine distance, the farther the distance, the greater the capacitance, and thus the greater the needle deflection.

Dimensions (WHD) 225 x 185 x 145 mm / 8.9 x 7.3 x 5.7 inch