- when add-noise is false, mute noise completely
- if the CommRadio is not powered by the generic electrical system,
work by default (as was previously the case)
Base class handles some common instrument features, such as the
serviceable node and electrical supply. The electrical supply node
and minimum voltage to operate can now be set in the configuration
via <power-supply>/path/to/output/volts</> and <minimum-supply-volts>