Hi,
Quick question: If I have two E1 ports (RJ45), then will running a straight ethernet cable between the two ports have the same affect as plugging a ballan into each port and using a pair of coax (over a v. short distance).
Likewise would using an ethernet crossover cable have the same affect as swapping the pairs round on one balland.
Or are the pinouts different to ethernet? I tried googling but couldn't find anything (perhaps because I can't seem to spell ballan 
).
Sam
Quick question: If I have two E1 ports (RJ45), then will running a
straight ethernet cable between the two ports have the same affect as
plugging a ballan into each port and using a pair of coax (over a v.
short distance).
You generally need a router or something else acting as store-and-forward.
E1/T1 and other plesiochronous circuits are just that, near synchronous,
and certainly not asynchronous. Things cannot be transmitted or received
without clocks on both sides being in synch, which may or may not be the
case if you try to hook up two arbitrary lines. Moreover, assuming both
are terminated towards you, both will be driving clock for your router
("terminal equipment") to pick up, and they are not going to be in phase.
Then there's the issue of different options for framing and various
control bits, etc. You might get lucky if you could convince one of the
circuit providers to take clock from you (which would then come from the
other circuit), but you would probably still need to deal with signal
level, framing, and other issues (ie, have a box of sorts). All in all,
an old cisco 2500 is probably the cheapest and most troublefree solution.
Or are the pinouts different to ethernet? I tried googling but couldn't
find anything (perhaps because I can't seem to spell ballan).
It's balun -- BALance-UNbalance.
Best,
-- Per
Whilst this is true, his question still stands. Yes indeed if you got the
RJ-45 crossover right (I don't think it's ethernet pinout from memory,
but...) you would indeed achieve the same effect as a crossed over pair of
coaxes. However, it might well not be the effect you intend or desire (for
the reasons Per points out).
One circumstance where this does work is connecting (for instance) an E1
trunk connection between (say) two FR switches in the same room, provided
you remember to set exactly one end to originate, and one end to receive
clock (i.e. where there are no carriers involved).
Alex
Fair enough. Pin-out is not the same as ethernet, but same idea; there's
a very clear diagram here about 2/3s down the page:
http://www.nettonet.com/support/docs/220-0000081_r01.n2n
  -- Per
In every case I've dealt with when setting up a back-to-back connection
of T1 or E1 circuits, the appropriate crossover connection between transmit
and receive (1,2 - 4,5 on 8-pin jacks, swap Tx and Rx on co-ax) and setting
one side to supply internal clock and the other side to recover clock from
line works just fine.
Quick question: If I have two E1 ports (RJ45), then will running a
straight ethernet cable between the two ports have the same affect as
plugging a ballan into each port and using a pair of coax (over a v.
short distance).
Not straight, you need to make or buy a special crossover cable unless
you're going from a CSU to a terminal equipment port, in which case a
straight cable will work if it has all four pairs connected. Some cheap
cables sold for ethernet use only have pairs 1,2 and 3,6 wired. These
will not work as T1/E1 uses 1,2 and 4,5.
Likewise would using an ethernet crossover cable have the same affect as
swapping the pairs round on one balland.
I think you mean "balun". A crossover cable for T1/E1 is pairs 1,2 and
4,5 swapped which is blue/white and green/white for 568A.
Or are the pinouts different to ethernet? I tried googling but couldn't
find anything (perhaps because I can't seem to spell ballan
Well, the modular jack connections are balanced and coaxial cable is
unbalanced. You don't need baluns unless you're going from BALanced
on one end to UNbalanced on the other (hence the name balun).
Get a straight-through cable. and look at it. If the insulation on the
left two pins is green when holding the contacts up and away from you,
then cut off one end and reassemble it with the green and blue pairs
swapped around. If orange, then swap the orange and blue. If brown, turn
it over and look again. 
Set ONE of your devices to provide clock ("Internal") and the other to
recover clock from the line ("Network"). If either of the devices is
also connected to a carrier or other network by T1/E1, clocking can get
more complicated and you probably want to consult a local expert on that
particular equipment.