> An E1 can be a long way from the box with the right cable. However many > people use the wrong cable. Using a LAN cable for an E1 often gives > errors if the cable is more than just a few metres long. Although the > plugs look the same, the twisted pairs should be grouped differently in > an E1 cable, and it really makes a difference. If the drop cable is only > a couple of metres long, a LAN cable is usually adequate. This is also > true for T1s.
Actually that's not entirely true. standard 568A/B wired cable does not split pairs for ethernet or DSX1 wiring. The problem is that DSX1 uses pins (1,2),(4,5) and ethernet (1,2), (3,6) (parenthesis show pairing). DSX1 must have the (1,2) and (4,5) pairs swapped to match the TX to the RX at each end, whereas normal ethernet does not, as the switch is cross-wired. Using an ethernet crossover cable does not help since it is swapping (1,2) and (3,6), not (1,2) and (4,5). The problem with using CAT5 for long telco runs is that the impedance is wrong at the line clock rate (~1MHz). IIRC the impedance for telco is specified at 600 ohms @ 1MHz, whereas for CAT5 the impedance is actually specified at around 100MHz, where the ethernet line rate is. You can get away with it so long as the impedance is right, but unless you've got the data sheets you're playing guessing games. Regards, Andrew _______________________________________________ Asterisk-Users mailing list [EMAIL PROTECTED] http://lists.digium.com/mailman/listinfo/asterisk-users
