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On Wed, 9 Oct 2013, Paul Sutton wrote:
Just looking at the Arduino starter kit thing on amazon one of the components seems to be a keypad http://www.amazon.co.uk/gp/product/B00BXXJDY2/ref=pe_502881_40420721_email_1p_1_im given that it only has 0 - 9 and A - D it can't be a hex keypad or that would have A - F maybe some Arduino hackers out there can shed light on what this is, or does the arduino use something other than hex Just out of curiosity, I haver seen numeric keypads, hex keypads but not one like this
It's a standard phone keypad.DTMF - Dual Tone Multi Frequency has 8 different tones arranged in a 4x4 grid. Each button sends 2 tones down the line. So you have capacity for 16 keys. The standard 0-9, star and hash (or box, octothorpe, square, or any number of other names that peopel tried to coin) as well as A, B, C and D.
I don't think A-D were never used on the PSTN, but were occasionally used for PABXs.
http://en.wikipedia.org/wiki/Dtmf Gordon -- The Mailing List for the Devon & Cornwall LUG http://mailman.dclug.org.uk/listinfo/list FAQ: http://www.dcglug.org.uk/listfaq