Hi PICSTER's.

I've posted this request before but unfortunately did not recieve many
replies.

This is my first time undertaking a microprocessor based project and have
ben advised that using a PIC for my particular application would be a good
start.

Basically what I'm trying to do is to use a PIC (16C74?) device to monitor
two ac voltage inputs. If either I/P exceeds it's predefined threshold over
x successive samples, then the remote monitoring device would establish a
modem link to a controlling point and report this.

It is envisaged that the controlling point would poll each of the remote
outstation at least once daily, no matter if any of them had alarmed back.
It is also the intention that the control point operator would be able to
select any outstation and be able to monitor the current status of thee
I/Ps.

The two I/Ps being monitored are very different and any suggestions as to
how I could best interface them to the pick would be appreciated.

Input 1: Very small ac noise voltage present in a telecommunications
circuit. The
voltage level is normally within the range 0.1 to 0.5 mV ac RMS and is
terminated in 600ohms. The signal bandwidth is 0.2KHz to 3.0Khz. This is
required to be put through a psophmetric filter prior to being sampled.

Input 2: The second signal is again an ac V but the magnitude ranges from
40V ac
rms to 400V rms with the alarm limit being 60Vac rms. This voltage is again
taken from a telecommunications circuit and is due to induction from
overhead power transmission lines. This voltage is normally measured with on
leg of the two wire circuit connected to Earth, and as such the i/p
impedence required is 1Mohm. The bandwidth required is 0.5 Hz to 5Khz
although this is under review.

The remote station must be capable of being addressed.