Is there a limiter on the PSM300 devices?
The P3RA has a volume limiter that is activated from the menu. The P3RA limiter attenuates the maximum volume output in 3dB increments between -3dB and -21dB. This is slightly different than the P9RA and P10R implementation where a maximum volume output can be selected between 3 and 9 on a 1-10 scale.
For optimal gain structure, the proper setup involves first bringing a good signal level into the PSM transmitter, then adjusting the input level, and then bringing the receiver's volume up to a comfortable level. If there is any excess headroom, with P3RA/P9RA/P10R, one can then set the volume limiter in the menu accordingly.
Starting with the PSM900, Shure has employed technology that mutes interference when detected. So instead of employing a limiter at x-dB SPL to prevent excessive noise from interference, the noise is attenuated.