Payphone triggers

We can detect a number of events taking place when someone interacts with the payphone. In your prototype designs, you should think about these as 'triggers' that can cause something to happen (like playing a sound, turning on a light, sending an email, playing a video, etc.)

Things we already know how to detect:

  • insert a US quarter
  • insert a US dime
  • insert a US nickel
  • we can tally up US coins - e.g. a trigger could be 'insert $1 in any coin combination'

Things we should be able to detect soon:

  • insert any other coin, US or foreign, or a slug
  • punch any of the 12 keypad buttons
  • we should be able to detect any sequence of key presses, like "#123*" or "LEIMERT" (5346378)
  • we may be able to detect a long press -- e.g. hold the # button for 10 seconds to unlock an easter egg.
  • take handset off-hook
  • place handset on-hook
  • we should be able to detect a "pulse" sequence (on old phones, you could press the hook 5 times in rapid succession instead of dialing "5") or morse code
  • speaking into the microphone on the handset. We probably won't do voice recognition but we can probably detect someone's voice above a certain noise threshold.
  • combinations of things: Like holding # while inserting a quarter.

Things which might require hardware modification

  • press coin release lever


  • Kevin: coin counter sketch done - it can interpret the input from the coin counter and add it all up - this is available on the wiki and could be loaded in a snap to any arduino board

Raspberry Pi

  • Andrew to port Kevin's work over to Pi (so we can use video, ethernet, etc.)

Back of front panel interactions

DTMF keypad input might be captured and interpreted / plugged straight into the innards of an older phone (theoretically). The circuit board behind the keys has an input that comes from the keys (looks like individual switches, so should be easily interpretable by Arduino).

Other outputs on the back of panel board:

  • REC (speaker?)
  • MIC
  • VOL (not used in the PROTEL application, it seems like the volume is set by a physical switch next to the red button on the circuit board)
  • Hook switch - registers whether the receiver is on the hook or not

Coin Counter

four wires - GWRB
  • G= ground
  • W = quarter
  • R = dime
  • B = nickel

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