> On Sat, 3 May 1997, Al Hopper wrote:
>
> > On a point 2 point circuit (usually) the telco does not supply clock. In
> > almost every other case the telco will supply the (sync) clock. Mr Jay is
> > indeed correct. Also the circuit pairs should be flipped somewhere in the
> > middle. Since you're seeing data the crossover must be OK.
>
> I keep getting conflicting advice on this...some say the telco provides
> clock, some say they don't. Is it possible some CSU/DSU's deal with
> incorrect settings better than others?...i.e. Say you have a PTP T1, with
> CSU/DSU's at each end set to slave/network. Will some CSU/DSU's handle
> this while others have a hard time?
Most of them will handle it - for a while. We had this problem with a
point-to-point MCI T-1 and Adtran TSUs. I made the assumption that the
circuit was de-muxed from a larger sync pipe and clock supplied by telco.
In fact, clock was not supplied by telco. Circuit came up, worked for
hours or days, and then froze. Telco getting in and looping would bring
it back, sometimes. Power-cycling one or both of the TSUs would usually
also bring it back. Eventually got someone at MCI to tell us definitively
that clocking was not supplied by them. Set one TSU to Internal, other to
Network, and it's been purring fine for years.
-- Jay Hennigan jay@west.net --
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