Flaky mic in TDD built in phone coupler - sources?

[Tony Duell]

> 
> On Sat, 1 Oct 2005 jpero at sympatico.ca wrote:
> > This is round 5/16" dia mic with felt screen stuck over the small
> > opening.
> > Now mic working intermittently and had to tap even bang on it to
> > wake up.
> 
> What kind of mike is it?

I assumed from the description and use that it was an electret condenser 
microphone.

> Some types are prone to "carbon granule clumping", and need to get shaken
> up and beaten on occasionally.

An old joke in the UK was to convince the chap at the other end of a 
phone conversation to sing loadly into the mouthpieces to free up the 
carbon granules. Didn't do a darn thing, actually, but you could get 
idiots to start singing.

One of my mad[1] friends is heavily into all sorts of old technology. I 
was chatting to him on the 'phone one time, and his voice started to 
become indistinct. I asked him to sing into the phone. He, of course, 
knew the joke. I head a few bangs, and then everything was fine again. 
He'd freed up the carbon granules in his microphone.

[1] Actually, all my freinds are mad...

-tony