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 do a "hard reset" and then initialize the clock with the current date and time.
This is done in the teminal mode by entering the DAYTIME command
24 hr. yy/mm/dd/hh/mm/ss (Hour as 00-24)
Eg. 24 hr time: DAYTIME 180601131523 (2018 June 01 13:15.:23)
24 hr. yy/mm/dd/h/mm/ss (Hour as 00-12)
Eg. 12 hr time: DAYTIME 180601011523 (2018 June 01 1:15.:23)
The RTC is read when the KPC3 is powered on or when the software hard 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 to preserve you other TNC settings.