Installing a Real Time Clock module
Here are 2 places that you can buy the RTC Modules from:
Kantronic's - FOX 72421
Digikey - EPSON RTC72421
The real time clock option for the KPC3 Plus (not the KPC3) is a self contained clock chip.
Disconnect the power and remove the lid of the KPC3 Plus and locate the empty IC socket (Note - the notch in the socket and the notch in the IC as in the picture)
Once installed power the TNC on and you will need to initialize the clock with the current date and time.
This is done in the teminal mode by entering the DAYTIME command
Eg. DAYTIME 180601131523 (2017 June 01 13:15.:23)
The RTC is read when the KPC3 is powered on or when the software reset it done.
Also a good Idea is to have a 9 volt battery with connector plugged into the TNC when not in use for long periods of time.