22 Mar
2001
22 Mar
'01
5:49 p.m.
On Thu, Mar 22, 2001 at 10:19:35PM +0000, Ron Buchalski wrote:
Forcing the 8th bit to a '1' isn't done to maintain timing.
Huh?
The 8th bit was forced to a '1' to maintain ones density on the T1 line. Early T1 specs did not allow more than 15 consecutive zeros to be transmitted because the T1 repeaters along the line rely on periodic pulses to keep their oscillators active. It was not a problem for voice circuits,
Yes, and this was necessary to prevent those repeaters from losing sync -- thus maintaining timing. --msa