Brush Development BL-202 2-Channel Magnetic Azimuth Elevation Oscillograph

Brush Development BL-202 2-Channel Magnetic Azimuth Elevation Oscillograph

The Brush Development BL-202 is a portable 2-channel magnetic oscillograph designed to simultaneously record azimuth and elevation data as continuous traces on a paper chart. Manufactured by The Brush Development Co. of Cleveland, Ohio, this instrument used galvanometer-based magnetic recording to capture real-time angular data — a technique common in military and aerospace tracking applications of the 1940s and 1950s. The portable, ruggedized case with carry strap indicates this unit was designed for field use rather than a fixed lab setting.

Specifications & What's Included

• Manufacturer: The Brush Development Co., Cleveland, Ohio, USA
• Model: BL-202
• Recording channels: 2 (plus Timer and Target trace channels visible on chart window)
• Measurement axes: Azimuth and Elevation
• Recording method: Magnetic / galvanometer paper chart
• Power: 115V AC, 60 Hz (per nameplate)
• Front connectors: J3701, J3702, J3703 (multi-pin military-style)
• Additional rear/side connectors: J3711, J3712, J3713
• Front controls: Power/fuse switch (marked FUSE), pilot indicator lamp (red), rotary control knob
• Chart window: Top-mounted, labeled Timer / Azimuth / Elevation / Target
• Form factor: Portable enclosed case with leather carry strap
• Paper chart: Present inside unit (visible in photos)
• Country of manufacture: United States

Applications

The Brush Development Co. was a pioneer in magnetic recording and galvanometer-based oscillograph instruments during the 1940s and 1950s, producing equipment widely used by the U.S. military, defense contractors, and aerospace programs. The BL-202 was designed to record the simultaneous angular position of tracked targets — specifically azimuth (horizontal bearing) and elevation (vertical angle) — as continuous paper traces, allowing post-event analysis of trajectory data. This type of portable oscillograph was used at radar tracking stations, anti-aircraft artillery test ranges, and early missile test facilities where real-time data capture in the field was required. The paper chart format, multi-pin connectors (J37-series), and ruggedized portable enclosure are all characteristic of U.S. military instrument design from the late 1940s into the mid-1950s. Today, instruments like the BL-202 are sought by collectors of vintage military test equipment, electronics historians, and restorers interested in early analog data recording technology.