[FedCom] Re: Unknown Frequencies (J Doe) - Is that your real name?

[Chris Parris]

Ken, I think he was referring to digital encryption over an analog repeater
system, i.e., DES. The CTCSS tone cannot be used while the encrypted
transmission is going through the repeater, but I believe that the repeaters
are opened with a brief preamble ( the short "chirp-chirp" sound before the
encrypted voice). The preamble is accompanied by the correct PL tone, so the
repeater opens and stays open for the length of the transmission.

NAC's are used with the P-25 transmission modes.

So it is possible to use CTCSS tones with a DES encrypted transmission, but
your repeater has to be able to deal with it...

- Chris
 --
Chris Parris
Fed Files Columnist
Monitoring Times Magazine
chrisparris at monitoringtimes.com
Fed Files Blog - http://mt-fedfiles.blogspot.com/


> Hmm that's interesting.  Isn't there something in digital called the
> "Network Access Code" NAC that is basically the same as ctcss/dcs?   I
> understand that there's thousands of NAC combinations.  Surely repeaters
> would want to be protected from unauthorized access.  HOWEVER, you are
> correct in that some FBI geographic areas (even in analog), more than 1
> repeater will repeat the same traffic.
>
> Ken