What happened to the Burst Modulator mode in the PSM-500/4900?
The PSM-500/4900 has the basic circuitry necessary to implement burst modulation. The burst demodulation scheme compatible with the modulation used in the PSM-2100 is no longer manufactured, and there is no clear standard for implementing this capability. Modifying the PSM-500/4900 to work with a specific burst demodulator scheme is an option which requires contacting the factory for availability.