[AusNOG] Reference clock for SDH network

[Lincoln Dale]

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.