I am going to organise a quest for teenagers.

I have a vintage phone like below:

enter image description here

I am looking for ideas how to use the rotary phone with numbers 1,2, ..., 9, 0 and letters A, B, C, F, H, I, K, L, M, R.

My attempt is: to use a "A1Z26" cipher (in my case A1R0), for instance, 3188 - CALL, 2188 - BALL, 619 - I AM, 4188 - FALL, 7688 - KILL, 2688 - BILL.

What is an alternative to the substitution cipher?


1 Answer 1


You can get a bit more excitement from the letters if you assign each number to a range, albeit an irregular one.

So 1=A, 2=B, 3=C,D,E, 4=F,G, 5=H, 6=I,J, 7=K, 8=L, 9=M,N,O,P,Q, and 0=R,S,T,U,V,W,X,Y,Z.

So for example PUZZLING STACK EXCHANGE becomes 90008694 00137 30351943.

To decode, reverse the process. With some of the letters fixed, guessing the others should be easy enough.

  • 1
    $\begingroup$ If the phone has actual letters marked on it, then using a different correspondence between letters and digits seems likely to be really confusing... $\endgroup$
    – Gareth McCaughan
    Dec 1, 2019 at 10:50
  • 1
    $\begingroup$ @GarethMcCaughan; fixed - it was very early... $\endgroup$
    – JMP
    Dec 1, 2019 at 11:30

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