mmm... letme see... I'd use a 20Mhz part like the 16C74 or a similar one.
A/D conversion time should be something like 16us (microseconds, please
don't start another thread on units here). That's enough for over 60000+
conversions per second. For telephony applications, 8000 conversions per
second is enough, so you have 125us to "process" each byte. That is about
625 instruction cycles in a 20Mhz part. Of course, that includes interrupts,
main program, and everything else.

Depending on how you plan to actually transmit the data over the phone line,
I'd say that you have a good chance of making it.

Now that I think about it, how on earth do you encode the digital data for
transmitting? Use a modem to handle the connection?

Regards
Andres Tarzia
Technology Consultant, SMART S.A.
e-mail: atarzia@smart.com.ar

-----Original Message-----
From: Ryan Pogge [mailto:pogge@SHORE.INTERCOM.NET]
Sent: Sunday, March 28, 1999 23:19
To: PICLIST@MITVMA.MIT.EDU
Subject: interesting concept


found this on a newsgroup
is it possible?

--snip--
I wish to build a device which could intercept an analogue signal and
convert it.

A/D Converter > PIC circuit > D/A Converter

The idea I have is to develop a "black box" which could effectively scramble
a telephone conversation making it totally private.  I would use the PIC
processor to perform the encryption.

I have written source code in 8086 which compresses data at bit level, I
don't think it would be convert.

My question being, could a single PIC processor work fast enough to perform
the algorithm in real-time?, I would assume 11Khz mono signal capabilities
would be sufficient.


Regards