I am improving on my first Arduino project (an office monitor). For the first round, I have wired an Arduino to a motion sensor. If there is motion it shows a green LED in the hall. If there is no motion it light a red LED.
I want to expand it further by sensing if the person is on a phone call (AVAYA 4621SW IP phone) and turn on a yellow LED. I need the means to be a simple plug in , tape on type solution. I am not willing to open up the phone to hack it. My first thought was to add a plug in extension to the hand set cord (not the network connection) to detect sound, but I am not sure how to do this with.
Any suggestions as to how to tell if the Voip phone is in a phone call?
Perhaps there's some way you can query the exchange to discover the engaged status of the phone? Some VoIP suppliers also use soft phones which implies the status can be determined from a client. That's the direction I'd be inclined to investigate for an elegant solution.
You mentioned using a 'tape on' approach. If you don't mind it looking naff, you could just add a second hook switch to the phone base so that your system knows when the handset is physically off-hook. That doesn't deal with hands-free operation, or soft phones, or use of any other phone.
For a more general solution you could just to use voice detection to determine whether anyone seems to be speaking in the office? Not perfect, but would cope with speaker phones and also with any other type of phone as long as the occupant speaks occasionally. If you have a microphone, you could do that on a PC.