North American Network Operators Group
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Re: Clear Channel on a T1

  • From: Majdi S. Abbas
  • Date: Thu Mar 22 17:56:10 2001 
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