While cleaning out his closet, Instructables user “Acmecorporation” discovered an old rotary telephone. Instead of tossing it away, the Maker decided to give the old-school device some modern-day technology using an Arduino Pro Mini and a SIM900 GSM shield.
Acmecorporation is able to use the aptly named TOWA Phone (There Once Was A Telephone) to make and receive calls, send single DMTF tones, and even program numbers on speed dial. Aside from its classic bell ringer, there’s an RGB LED that indicates GSM status: red for offline, green for online, and blue for an incoming call.
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