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DTMF Encoder

DTMF Keypad Encoder kit

Inter digit holding time of 1.5 seconds

Gold plated PCB

16 key Keypad optional

In Stock

 DTMF Encoder kit shown with optional keypad


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.


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.


dtmf encoder video

Buy this item

DTMF Encoder only £13.99
DTMF Encoder + Keypad £20.98

What's in the Box

A compact Gold Plated PCB, components and programmed PIC. See the PDF for instruction details and component list.


The keypad is optional as this kit will work with most matrix keypads, the order of pin out varies between keypads and this should be checked if using a different keypad.

You can connect the keypad via wires if desired, often necessary with other keypads.

Note: Keypad has white keys with black numbers as per photos, NOT as per video

Purchase our 16 Key Keypad below:

Buy this item

Keypad £6.99


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