[AusNOG] Reference clock for SDH network
Lincoln Dale
ltd at cisco.com
Tue Oct 27 15:27:59 EST 2009
On 27/10/2009, at 1:57 PM, Damien Gardner Jnr wrote:
> I'm obviously missing something here, but how on earth can a
> crystal, a couple of caps and resistors, and maybe a transistor or
> two or an IC work out to the $3k mark??
>
> I'm assuming you're actually looking for something more complex than
> a simple 2mhz clock signal??
yes, the spec is that it has to be better than +/- 20PPM which means
most of them are temperature-compensated and in fact many are oven
controlled.
furthermore, the expectation is that said clock source probably has a
high lifespan (which rules out most clock source equipment) as most
oscillators have a change over their lifespan of between +/-1-5PPM/
year, and while one could replace said clock, often its the "weakest
link" of the entire network, i.e. where failure is not an option.
because of that, there is often much additional electronics for
standby or redundant clocks - which all amounts to additional cost.
cheers,
lincoln.
More information about the AusNOG
mailing list