Re: telemetry question
The only information I have ever found on this subject is in old books available on used book web sites. Try searching bookfinder.com with telemetry entered in the title search rectangle. These older systems were all analog.
What I think is happening in the more modern telemetry is that ordinary digital transmission methods are being used and sensors with digital outputs are supplying the data. At the receive end the data is stored in files and possibly displayed in real time.