[sci.electronics] How to detect phone ring w/o connecting circuitry to phone?

rdi@cci632.UUCP (Rick Inzero) (09/01/90)

Here at work, we've got these new fangled Northern Telecom "Meridian 1" 
system phones.  They aren't REAL phones [:-)], but are digital, going 
over fiber optics throughout the building to our own (?) digital switch.
Anyway, being digital, each and every phone has EXACTLY the same ring.
Everybody's phone sounds exactly the same, so when you are in a meeting
in someone else's cubicle, and a phone rings, everybody has to leave
to check if it's theirs.  I've tried to come up with some way to detect
the phone ring, but am hampered because:
 -The switch is "smart", and I a cannot unplug the phone from the wall 
or else my phone will go permanantly dead until the system operator fixes it.  
 -Because it's digital, you couldn't put some simple analog circuit
ring-detect between the phone and wall jack anyway and still have it work.
 -There is no electro-magnetic bell ringer, just a wafer thin speaker that
produces the warbling "ring", and also acts as a receive-only speaker phone.
Putting a capacitor across the speaker works, producing a different,
extended tone rather than the warbling ring, but I think the phone is
smart (or dumb) enough to think that something is awry, and it only
"rings" audibly once.  The phone is still "ringing", only it doesn't 
announce it.
 -The electronics in the phone are all surface mount; no where to easily
clip on a lead or two to "experiment".  I certainly don't want to use 
a soldering iron or otherwise damage this phone.

What I've been thinking of is something that would close a relay to complete 
a separate battery powered "buzzer" circuit (that way it would basically use 
no power except to ring the external buzzer).  On a "real" phone, I'd simply 
tape a magnetic reed switch to the bell coils, but that won't work with this 
phone.  SO, I need to figure out some way to either "listen" for an actual 
sound that the speaker produces, or detect when the little flashing 3/16" 
LCD "arrow" appears that also signals that the phone is ringing, and use
this to close the relay.

Any fresh ideas on how to accomplish this?

---
Rick Inzero				        rochester!cci632!rdi
Computer Consoles Inc. (CCI)			uunet!ccicpg!cci632!rdi
Rochester, NY					uunet!rlgvax!cci632!rdi

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