Connect Morse Key to Iphone

How to connect morse key to an iPhone? Using the buttons on the standard headphones does not work, as the apple interface does not provide low-level access to low-level events like button-down. The idea (R1, R2) will be (1) put a signal to one stereo channel (2) receive the same signal on the input channel (small resistor will simulate mic) (3) detect tone level changes for input channel -> real time-morse (4) put side-tone & co to remaining stereo channel.

Pasted Graphic

  • 1(Tip) – Key (Ground)
  • 2 – Ear (Contact)
  • 3 – Ear (Ground)
  • 4(Ground) – R2(46,6k) – Key 1
  • 4(Ground) – R3(22k) – Key 2
  • 4(Ground) – R1(1k) – 3

I got a prototype running with irmc-ios (R4) and the same physical interface also works with iMorsix (R3).

(R1) Hijacking Power from […] Audio Interface
(R2) Sources: hijack-main
(R3) App: iMorsix
(R4) App: irmc-ios

Morse Decoder Test – iPhone / iPad

There are three morse decoders in the App Store. Same test case for all of them: “CQ CQ CQ DE DG
D6FL DG6FL K” from memory of my palm paddle¬†with 20wpm.


  1. MorseDecoder (HotPaw Productions)
    Seems to work
  2. MorseDec (Luca Facchinetti)
    Room for improvement
  3. Morsepad (Black Cat Systems)
    Does not work at all