Servo has a long history in the railroad industry as one of the premiere producers of hot box detectors. Founded in 1946, their
themal sensing technology quickly proved valuable to railroads for detecting hot boxes.
Most of Servo's defect detector models were not of the talker variety. Models such as the 7621, 7707, & 8808 simply printed results remotely at a tower, dispatch office, or elsewhere - any defects found would be relayed by radio to the train crew. In the case of Conrail, Servo's units were so predominate that the clerks whose job it was to check print-outs for defects were known as Servo Clerks.
In 1994, Servo Corporation sold their Transportation Division, comprised of their defect detector line, to Harmon Industries.
A predecessor to the far more common Servo 9000, the Servo 8909 had a much more robotic sound. Aside from the N&W/NS Trackside Analyzers, most did not last particularly long in the field. Common users include Canadian Pacific, Kansas City Southern, Norfolk & Western, and Norfolk Southern.
Introduced in the mid 1980s, this was by far Servo's most popular talker model prior to the product line's acquisition by Harmon Industries. Production of the Servo 9000 ended in December 2002. Common users include Canadian Pacific, Chessie System, Conrail, P&LE, Santa Fe, & Southern Pacific.
Conrail Servo 9000 Plans