crystals in series or parallel

[walid]

In some circuits I see four 20MHz crystals in series or sometimes in parallel!
What's equivalant value then?

[Guest 1st Mil-Tech]

oscillator crystals in series would only pass the frequency designed for the crystal to oscillate at.

In parallel they would block only the frequency of the crystal.

I think what you are asking is maybe a complex crystal matrix, which I have no firsthand answers. A diagram or application would help.

[Staigen]

Hi

I belive he means a crystal filter!

//Staigen

[Guest 1st Mil-Tech]

Try this link:
http://www.radio-electronics.com/info/data/crystals/monolithic_crystal_filter.php