Telephone Extension Ringer How Do I Add A Telephone Ringer Only To An Extension Jack?

How do I add a telephone ringer only to an extension jack? - telephone extension ringer

I have a multimeter, and I'm ready to solder! I wish to take an unused expansion slot within four business telephone and cable finger at them, so you can put the bell in another room to hear the phone when it rings. Is it just a matter of fixing a piezoelectric buzzer? Can I have the same lines blinking light, you can out there? Soooo .... Son of color that you use when you insert a plug into the outlet and pulls the threads out?