DTMF ENCODER kit

Inter digit holding time of 1.5 seconds

Gold plated PCB

16 key Keypad (optional)

Encoder only £15.99
Keypad only £6.99
Encoder + Keypad £22.98

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.

FUNCTION INPUT

If you choose, you can ground the function input (see circuit). The encoder then encodes the 8 tones used in DTMF as single tones when pressing buttons 1 to 8. This is useful for checking the frequency response of connected audio paths or transmitters/receivers etc.

The complete kit of parts includes a pre-programmed PIC micro and gold plated PCB.

RF

The PCB has been designed with pads on the back for 1nF 0805 ceramic capacitors for RF decoupling on all inputs and outputs if needed, these are not supplied and not expected to be needed unless you use it in a high level RF environment.