The 970-HA-JOKES Payphone Project
Nate 
Where Do You Get a Payphone?
While there are a variety of payphones on ebay at flea markets, it’s very tricky to find a legitimately procured payphone. Also, it’s next to impossible to find one with locks. To save time, but at expense, I ended up getting a PP100 with an L31 Enclosure and floor mount pedestal for a little over $1000 shipped from payphone.com. I didn’t need a truly functional payphone since I was going to mod the heck out of it, but being able to order keys and locks along with the phone, shroud, and pedestal saved me tremendous amounts of time and frustration.
Learning how the phone worked was another challenge. There are incredible forums and piles of resources available (Vintage Arcade Preservation Society, Classic Rotary Phones Forum, among many others), but as with most hobbies and bygone professions, the acronyms are impenetrable and ‘where do I start?’ tutorials are non-existent. In summary, the main controller board detects when a valid coin has passed the coin detector, and transmits tones back to the phone switch. Power is provided via the phone line itself (sometimes fed by local power as well). When the correct amount of money is detected, the call is connected to the phone network.