With our DTMF Encoder kit you can encode all 16 DTMF tone pairs directly from a keypad as well as 8 single tones. Generate tones for as long as a key is pressed; the tone audio output from the HT9200 encoder IC is amplified, buffered and filtered before the output level control, improving the overall quality of the generated signal.
You also have a transmit keying open collector output (active low) which activates on first key press: it has an inter-digit holding time of 1 or 1.5 seconds to keep the transmitter on between key presses. Fit the jumper to CN4 to reduce the delay to 1 second, otherwise 1.5 seconds is used.
It runs from 7 to 16V DC at a few mA.