Otherwise it is disabled. Also, you can connect several radios that are active on the same band. In these cases, it is not possible, or not a good idea, to transmit on more than one frequency. This transmitter will only be keyed when the carrier detect of all other interfaces in the group is off. A byte that can be used to define different groups.
Interfaces are in the same group, when the logical AND between their xx values is nonzero.
When 2 interfaces use group 201, their transmitters will never be keyed at the same time. When 2 interfaces use group 101, the transmitters will only key when both channels are clear at the same time. When group 301, the transmitters will not be keyed at the same time. Don't forget to convert the octal numbers into decimal before you set the parameter. Useful for a very slow squelch.