You are hearing a Motorola Quik-Call I (QCI) tones (think of the old show Emergency!).
Rockland uses a mixture of QCI and DTMF tones for fire station alerting. These tones activate a QCI or DTMF receiver, which in turn triggers a relay that re-encodes the Quik-Call II (QCII) pager tones from the local firehouse base station, as well as activates any horns or whistles the firehouse may have.
These are not used to alert pagers, as no modern pager is QCI capable. As the old QCI firehouse decoders are dying off, they are being replaced with modern DTMF decoders. There is a mixture of Plectron, Motorola, and Federal Signal QCI decoders still in use, some dating back to the 60s.
Rockland has been using QCI tones for many decades. Up to just a few years ago, all 26 fire departments in Rockland used QCI tones, however that is now down to 16 departments. 10 departments have switched to the newer DTMF format for the aforementioned reason.
All pager tones in Rockland are QCII format, although not necessarily from the Motorola tone plan. Many use Plectron or Federal Signal tones as well.
All fire department dispatch tones in Rockland on 46.18 MHz and 470.800 MHz are encoded by 44-Control's MCC 7500 consoles in the 911 Center at the Fire Training Center in Pomona. This includes the QCII pager tones, the QCI station tones, the DTMF station tones, and the Knox DTMF tones.