[Asterisk-Users] E1/T1 failover hardware

[John Daragon]

Jon Pounder wrote:
>>Warning ! I know zip about electronics.
> 
> 
> why not just use a multipole relay ?
> 
> a 4pole double throw relay gives you 4 sets of contacts for the 2x tx and
> 2x rx wires. if you want to control with a bit in a parallel port, use
> something like a uln2003 relay driver (if the coil current is low enough),
> or a couple discrete transistors with the right gain and power handling.
> 
> use the 12vdc out of a spare drive connector to power the relay.
> 
> I would use one relay rather than 2 dpdt ones so that the switches are
> mechanically locked together and if one relay sticks you don't get a weird
> combination of circuits connected. Nothing will break, and the phone cops
> won't likely bother you if this does happen, but it could be real annoying
> and hard to diagnose if it does.
> 
> This is basically the electromechanical equivalent of you pulling one
> cable and plugging in another (which is what I was going to do with some
> T1 routers), except, I found the TXPort.

Good idea.  I just have an irrational dislike of moving parts. And I 
*like* MOSFETS !

> This actually is meant for failing between telco circuits, but works just
> fine working failing between CPE instead. it actually has csus, reframers,
> clock generator etc, as well as the "relay" circuit I describe to do the
> switchover. it actually samples the lines and uses some intelligence to
> see which to switch to. The device is "obsolete" so you'll only find it
> surplus now, and its t1 only as far as I know but there is probably E1
> gear around that does the same thing. I bought mine for $20 so it was not
> even worth thinking about my own setup for that price, but they were
> listed at up to $3000 when new.

I've only had a quick look for these, but E1 ones seem to be thin on the 
ground and expensive, and I have a horrible feeling that all the 
reframing stuff just adds another set of variables if something goes 
wrong somewhere.

Thanks again.

jd

-- 

John Daragon                                          john at argv.co.uk
argv[0] limited
Lambs Lawn Cottage,  Staple Fitzpaine,  Taunton,  TA3 5SL,  UK
v +44 (0) 1460 234068   f +44 (0) 1460 234069   m +44 (0) 7836 576127