DTMF Generator

Purpose

The DTMF Generator is a very simple device for testing the DTMF Decoder.  It is constructed with two Sine Wave Generators and a set of buttons (which are simply copies of the Sine Wave Generator's Frequency control).  When you press a button, three things happen.  First the mute on the mixer that combines the two Sine Waves is unmuted (it is muted whenever no button is pressed).  Second, the top Sine Generator is assigned a Low Tone (697Hz, 770Hz, 852Hz or 941Hz) and Third, the bottom Sine Generator is assigned a High Tone (1.21kHz, 1.34kHz, 1.48kHz or 1.63kHz).  These tones, when combined in specific combinations form the 16 different possible combinations of DTMF (Dual Tone Modulated Frequency).  Your typical telephone includes 12 of the 16 combinations.  A, B, C and D were used internally by the phone company to trigger their own equipment (such as to command a pay phone to drop a coin into the change slot for a customer.  With much more sophisticated equipment in place this will not work today).

This is not a sequencing device.  You won't be able to pre-program a string of numbers and then trigger them to be played back later.  Like the first sentence says, this device was created to test the DTMF Decoder or any other DTMF triggered device.