Bearing & Wheel Scanners
Precursor to the well-known ACS scanner, the 8909 scanner was common to pre-talker detectors. Sites later upgraded to Servo System 9000s often kept these older scanners, with some remaining in active mainline service into the early 2000s. They could also be found in use with other manufacturers' detectors, such as Harmon.
Servo/GE Transportation/Progress Rail ACS
The ACS (Advanced Concept Scanner) is the most common type of scanner found on today's railroads. It replaced the 8909 scanner in the
1990s, and remains relatively unchanged in appearance today, even as it changed ownership from Servo to Harmon to GE Transportation & finally to Progress
Rail. Older examples had the Servo logo cast into the housing; contemporary units are unbranded.
The ACS scanners were used on Servo 9000, Harmon Cyberscan 2000, and GE/Progress Rail MicroHBD detectors. Additionally, they were used on Devtronics CMA02 and Harmon Model 75 detectors (from the days before Harmon owned either Devtronics or Servo).