A telephone shield for Arduino Uno. For rotary dial phones, rings 1 to 6 private phone lines from any phone. Includes Gerber files to make a PCB. Uses 8 relays, 6 of which are for incoming phone lines, 2 for switching Uses a "Black Magic" 12v to 86vac 20 Hz ring generator available on eBay (old stock). See Instructables https://www.instructables.com/Rotary-Dial-Telephone-Exchange/