Not sure if these are intentional, but there are two AWS Ramps, on the Down side, just before Stonebridge Park, on the Watford DC Line (WCML Euston - MKC). They are both on the same line, within a few metres of each other, and both gave a tone to the corresponding signal at the end of Stonebridge Park station.
Something else I have noticed on one or two of the signals, there is one I know of for certain that, when showing a Green aspect, gives off a warning tone passing over the AWS Magnet. It is located on the Up line after leaving Bushey on the Watford DC Line, WCML Route.
