The WBS-680 wireless intercom systems have a total of 48 frequency groups, only 12 groups are user programmable.
The first 36 frequency groups are factory defined and therefore are not adjustable by the customer via the programming menus on the base station or beltpacks.
The first 24 factory defined groups are paired as A and B groups, thus allowing for 2 basestations and up to 8 beltpacks to be paired together with frequencies that will not cause intermod products. For example, if group 01A and 01B are selected the base station frequencies will be the same but 8 different beltpack frequencies will be selected. This will allow for two linked bases to work together will only one base station transmitting, the 2nd base will need to have it's transmitters disabled.
The remaining 12 factory defined groups are normally intended for only single system use (1 basestation and 4 beltpacks).
The last 12 frequency groups are user programmable and initially are left blank. They are editable in 25kHz increments within the 18MHz transmit and receive frequency band designated for that basestation or beltpack.