Basic, But Somewhat Technical Question

[wb0wao]

I have been studying some of the non-scanner supported digital formats being used - MotoTRBO and NDXN in particular. One thing that I did discover is that there are a vast number of "privacy codes" that can be entered into a radio at the time it is programmed by the tech. I am specifically not refering to any type of added on encryption that could be used by the end user, i.e. an added board using AES encryption or by the encryption option that comes standard with the radio.

Now here is the question - do these privacy codes modify the transmitted signal so that the signal is fundimentally different from another signal of the same type, but using a different privacy code?

OR....

Is it a hardware specific system in which the radio properly decodes the transmission, but the radio will not "pass it through" because the privacy code is different? Basically operating like CTCSS/DPL does now?

Dennis

 

[SCPD]

Hi Dennis;

The short answer is - both. Some systems include an ID number with the voice data. When the radio sees an ID it has been progammed to accept - it passes audio through. Conventional P25 works this way. Other systems shuffle the bits around. Recovering the audio requires unshuffling the data before it can be decoded into audio. This resembles shared secret symmetric encryption. I don't know what TRBO or NXDN use.