What powers your intercom? something you can steal power off of?
a microprocessor will run a while on a battery. You'll probably need a
higher voltage to run your relays and lights....plenty of ways to go about
this.

I like the microprocessor idea. www.parallax.com sells good kits for people
that don't need to know much. Great support and plenty of documentation!


"Form@C" wrote in message
news
On Mon, 26 Apr 2004 19:30:20 +1000, Gaz Man wrote:

Hi all. Thanks in advance for any help you can give. Please note my
email
address is invalid - this is to stop spam. Reply to gazman at pobox dot
com to email me directly.

Here's my problem :

My front gate is 150M from the house and I will have an intercom and
system to open the gates, turn on the lights, etc etc.

I ran two Cat 5E cables (total 16 conductors) underground. Somehow one
of
the cables has been cut, so I have only 8 conductors left. The intercom
requires 5 of these, so I have just 3 conductors to control the gates,
lights, fountain etc as well as send a signal back to the house to
indicate what position the gate is in.



Isn't it actually worse? How are you going to power the decoding
electronics at the remote end? Can you get another supply or are you stuck
with ground, supply & a single data line?

Having said that, I'm sure it can be done. I've seen an alarm chip that
used the supply line for bi-directional data transfer on a 2-wire system.
Only a couple of i/o each way though IIRC.

7-segment LED display drivers look good for remote output shift registers
- with about 32 outputs!

--
Cheers...
Mick
Gave up on viruses & trojans - moved to Linux... :-)
Nascom & Gemini info at http://www.nascom.info