Check out the Intercoms we sell for 3 wire systems. If you want a complete do it yourself kit, we recommend you look at our packaged solutions, the Audio Tech and DMC3-4 kits. Otherwise, you can look at the Nutone and M&S intercom solutions we recommend for your 3 wire system. Don't hesitate to call us at 800-221-8227. We are always ready to help you find the intercom that will meet your specific needs.