CSX STC SmartScan

Southern Technologies Corp. (STC) has 3 generations of hotbox detectors: the Sentry System, the SmartScan NG, and the SmartScan NG². Non-heat detecting models included the Sentry System (black casing, whereas heat detecting models had a blue casing), the Small Talk, and the iCUBE.

The Sentry System and the SmartScan NG both use the same voice (that of STC employee Paul Shenefield), which can make it easy to confuse the two. The Sentry System has a slightly muffled sound, a quicker pace, and the tendency to say "dot" instead of "point" for the milepost location. Additionally, the SmartScan NG was introduced in 2004 as the successor to the Sentry System; by the time of this writing in 2021, most Sentry System units have been retired from mainline service.

-Information courtesy of Nick Wilson from defectdetector.net