AVR-Chat

Peter Gargano wrote:

> Re: [AVR-Chat] Source of Caller ID Chips
> 
> Kathy Quinlan wrote:
> 
>>Peter Gargano wrote:
>>
>>>This thread reminds me of a project I'd like to start (if I had the time). I 
>>>want a simple, intelligent, 3 (up to 8) line PABX (Private Automatic Branch 
>>>eXchange) using "normal" phones.
>>>
>>>Maybe someone has seen a DIY PABX somewhere?
>>>
>>>Peter
>>
>>Yeah, I have designed many PABX's over the years, Some used special 
>>handsets, others stock standard 48V handsets.
> 
> 
> I was thinking of something simple that (if possible) used the standard AU 
> Telstra phone (ie. 48V tone dial). All I'm after is something that would allow 
> anyone to pick up a call on one or two lines, and transfer it to another line 
> (up to 7 other lines).
> 
> To be honest, I have not done any homework on what's required to do this. I 
> figured someone else had maybe done something similar that could be adapted, 
> so I didn't have to start out from scratch.
> 
> And yes, I know the biggest issue is one of safety, and I was thinking that it 
> could be powered from a battery that could be recharged periodically, so no 
> direct connection to the mains. A 5 or 6 Volt to 48 Volt supply is pretty easy 
> to organise.
> 
> 
>>First you need to decide what you want, as some features are not easy to 
>>impliment without custom parts, my last one I designed for a specific 
>>aplication used SLIC's (Subscriber Line Interface Circuits) out of an 
>>old NEC PABX (D3 or in au Telecom system 120) as these handle all the 
>>line conditioning, ring and tone switching etc.
> 
> 
> Kat, are any of these designs in the public domain?

Nope, all the designs are behind NDA's due to the cost of the permits 
for them :(

But I can advise on design issues to maximise safety etc, I would not 
worry about running on batteries, they will not last long (unless you 
are talking a big battery) It is very easy to design for safety, just 
make sure you use lots of isolation transformers and relays etc.

I can provide some schematic snipets of line and phone interface 
circuits, and if you are in WA I can probably give you some SLIC's etc 
from NEC as I have a fair few (ummm well most of the Spares in WA for 
the D3 series)

Regards,

Kat.


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