This applet is copied directly from a page created by Dr Iain A Robin. The original page is located at www.dsptutor.freeuk.com/dtmf/ToneGenerator.html. Permission to copy is granted in the downloadable code and is stated as follows:
Java source code for DTMF Tone Generator applet (C) 1998 Dr Iain A Robin This code may be used for any non-commercial educational or scientific purposes, although acknowledgment of its origin would be appreciated. Note that this is Java 1.1 code and must be compiled using a JDK 1.1 compliant compiler. If you have any queries about the applet code please e-mail i.robin@bell.ac.uk
The applet generates DTMF (Dual Tone Multi-Frequency) tones as used on TouchTone phones. The number can be dialled by clicking the appropriate buttons on the keypad or pressing the keys 0 - 9, *, # etc on your keyboard. Alternatively, click in the text field and type in the phone number, then click "Dial". If you hold a TouchTone phone close to the speaker, the tones should register as if you dialled them on the phone keypad.
Note that the applet works much more effectively if you have a sound card. If you don't, you just have to hum the tones yourself.
The keys A, B, C and D shown on the keypad generate tones in accordance with the TouchTone standard. These keys are not normally found on telephone keypads at present, but may be used in the future.
See the original page by Dr. Robin for more information.