One option for making text entry easier is to use a QWERTY keypad (Fig 1 ). This type of keypad employs 40 or more keys versus the normal 12 in a DTMF handset. Although the additional keys make the ...

This type of keypad employs 40 or more keys versus the normal 12 in a DTMF handset. Although the additional keys make the handset larger and involve more electronic components, text message users may ...

[Guy] used a SparkFun RP2040 to handle input from the DTMF keypad and play the tones, the dial and busy signals, and the various recordings into the ear of the receiver.

Though many of us will never have experimented with it, most readers should be familiar with DTMF as the tones used by the telephone system for dialling. If your youth was not misspent mashing 4-4-… ...

This circuit uses the HT9170 DTMF receiver which processes the signal from the mobile phone’s DTMF keypad. The HT9170 decodes the 16 DTMF tone pairs into a 4-bit BCD code output. The 74AHC04D, a ...

Bendix King Digital P25 APCO - 512 Ch, 6 Watt, VHF 136-174 MHz Portable Radio available with or without Full DTMF Keypad (NOT Upgradeable to Trunking) Check out the KNG P150S digital portable radio.