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DTMF-ENC16 is an inexpensive, self contained, DTMF (dual tone multiple frequency) encoder board with a full size 16 button keypad. The board has a standard RCA audio out jack and can either be powered with a 9 volt battery or through the 2.1 mm DC IN jack.



  • Dimensions: 2.8" x 3.0" x 1.5"
  • Weight: 4.2 oz. (without 9 volt battery installed)
  • Input voltage: 8.0 to 14.0 volts DC (17ma max, 10ma idle)
  • Operating temperature: -20 C to +60 C
  • Output Level:   Line Level 0 to -5 db (default),   Mic Level -45 to -50 db
  • Button contact life: 1,000,000 cycles per key
  • Keys: 0123456789ABCD*#


    The audio output level can be set to microphone or line level via internal jumper J1. To access the jumper remove the four screws on the two sides of the enclosure.
    Jumpered: Line Level 0 to -5 db (default)
    Unjumpered: Mic Level -45 to -50 db



    While pressing any one of the 16 keypad buttons a mixture of two sinewave tones are generated on the "AUDIO OUT" jack. (e.g. pressing "9" produces a simultaneous 852 Hz and 1477 Hz tone).If two or more buttons on the same row or the same column are pressed simultaneously then a single sinewave tone is generated.  (e.g. pressing "1" and "4" simultaneously produces a 1209 Hz tone, pressing "3" and "A" simultaneously produces a 697 Hz tone).

      1209 Hz 1336 Hz 1477 Hz 1633 Hz
    697 Hz 1 2 3 A
    770 Hz 4 5 6 B
    852 Hz 7 8 9 C
    941 Hz * 0 # D

    Note: Never attach both DC sources at the same time. (i.e. 9 volt battery and power on the "DC IN" jack)

    Troubleshooting Tips:

    Problem Solution
    Green LED off (won’t power up) Verify power switch is in "ON" position.Verify battery voltage (8 - 9 VDC) or "DC IN" power supply voltage (8 - 14 VDC).Verify battery or "DC IN" +/- polarity correct.
    Output tones distorted Verify battery voltage (8 - 9 VDC) or "DC IN" power supply voltage (8 - 14 VDC).


    Warranty & Service:

    If the product fails to perform as described in our product description or specification, within 1 year from the date of shipment to the buyer, we will repair or replace the product and/or accessories originally supplied. Failure due to improper installation, misuse, abuse or accident is not covered by this warranty. Incidental and consequential damages are not covered by this warranty.The buyer must obtain a Return Material Authorization by calling (248) 588-4400, and shipping the defective product to Intuitive Circuits, 3928 Wardlow Ct., Troy, MI 48083, freight prepaid. After the warranty expires, we will promptly supply an estimate for the repair cost.