47 CFR 80.877 - Controls and indicators required for VHF radiotelephone installation.
The controls and indicators used on equipment of the VHF radiotelephone installation must meet the following standards:
(a) The size of controls must easily permit normal adjustment. The function and the setting of the controls must be clearly indicated.d
(b) Controls must be illuminated to permit satisfactory operation of the equipment.
(c) Means must be provided to reduce to extinction any light output from the equipment which could affect safety of navigation.
(d) An on/off switch must be provided for the entire installation with a visual indication that the installation is switched on.
(e) The equipment must indicate the channel number, as given in the Radio Regulations, to which it is tuned. It must allow the determination of the channel number under all conditions of external lighting. Channel 16 must be distinctively marked.
(f) The receiver must have a manual volume control and a squelch control.
(g) If the external controls are on a separate control unit and more than one such control unit is provided, the one on the bridge must have priority over the others. When there is more than one control unit, indication must be given to the other(s) that the transmitter is in operation.