26 Mar
2007
26 Mar
'07
8:37 a.m.
Chuck Guzis wrote:
On 25 Mar 2007 at 21:30, Jay West wrote:
A company I used to work for had numerous direct-wire
connections of this sort.
You could get either 2-wire or 4-wire (2-pair) connections. We
always used the 4-wire (2-pair) option. You could then attach a
"short haul modem" on each end to get a serial line that would
work up to 9600 baud, depending on the distance.
One of the biggest problem we had, was the phone company
inserting "transformers" in the leased lines. They would do
this on their own initiative. This would cause the modems to
quit working. After getting them to remove the transformers,
we would have to re-determine the pairs.
One end MUST be a digital connection. For 56K,
on the ISP end, the line must be ISDN, PRI, etc. Regular analog POTS line
won't work on the ISP end. In ADDITION, there can't be more than one analog
to digital transition anywhere in the circuit from source to destination.
Bridge clips will also invalidate 56K connections on POTS lines.
Apropos to the vintage aspect...
Telcos used to (maybe prior to 1990) offer copper-to-copper
connections for things like fire and burglar alarms. Some
enterprising souls were making a go of using these connections
instead of ISDN (probably over a short haul, it might work). I was
surprised at how quickly all of the RBOCs got rid of the all-copper
arrangement.