This vintage british telephone from Betacom was completely transformed into a real lo-fi microphone. All the transformation was professionally done, including good quality parts. It connects with a regular jack cable from the output, directly connected to the original mic. It also plays the keys, with a kind of 8 bit sound! It has a second jack output for those notes. For getting those notes working, you should use a 9V or lower power supply. To avoid noises, it may require a DI Box with Ground Lift. I have plenty of other vintage phones ready to transform. I can transform them by request, with your personal specs