Note:The CA10 & CS10 have been discontinued for 5 years. Recommend a new OfficeRunner! :-)
You should not have to adjust the channel settings unless you experience cross talk. (Cross talk is noise from one telephone line that is audible on another line. It can occur when the bases are too close and on the same frequency.)
If you do experience cross talk, then adjust each unit to a different channel.
The channels are controlled by the 2 dials on the back of the CA10 / CS10. There are 39 possible channels. If the dial on the left is on 2 and the dial on the right is on 5, you are effectively at 25. So while the dials have 99 positions, any setting higher than 39 is effectively 39.
If the channel is set to “00” the unit will roam onto the first available channel. After adjusting the channel, you must turn the headset remote off and on again while it’s in the base to “reset” it to the current channel.