-DTMF TESTER V1.0- -Fast Fourier Systems - WARNING : This program should only be run on a Psion Series 3A. It may cause a crash and loss of data if run on any other machine. INTRODUCTION : This program samples a sound (specifically DTMF tones) via the Psion 3A microphone and determines the frequencies which make up the tones. A DTMF tone consists of two frequencies. These frequencies differ for different digits in accordance with the following chart : 1209 1336 1477 697 1 2 3 770 4 5 6 852 7 8 9 941 * 0 # Thus it can be seen that "1" is represented by the frequencies 697 hz and 1209 hz, "8" by 852 hz and 1336 hz, "*" by 941 hz and 1209 hz and so on. These frequencies and certain other parameters for DTMF are governed by CCITT recommendation Q.23. The other parameters include power levels and the ratio in dBs of one frequency with respect to the other. DTMF has evolved slightly differently in different countries and so, for example, frequency tolerances vary from country to country. Thus CCITT does not give definitive tolerances but gives examples of tolerances in various countries. MEASUREMENTS AND TESTS The program examines the parts of the frequency spectrum involved with DTMF tones and reports back on the frequencies it has detected, and compares these with the CCITT recommendations. It also reports on the ratio in dBs between the two DTMF frequencies. It performs the following tests: 1. Are the two frequencies within 2% of the CCITT rec ? 2. Is the dB ratio < 5 ? and reports on whether or not the tests have passed. The program can measure frequencies to plus or minus 4 Hz. A spectrum is shown to indicate how pure the frequencies of the DTMF tone are. The DTMF digit sampled is also displayed. INSTALLATION Install the file DTMFTEST.OPA in the APP directory. Install the file SYS$SAMP.LDD in the root directory. (Please note the information about this file given below). Install the Dtmftest application using Psion-I from the system screen. The program requires 85k of free memory to run. SYS$SAMP.LDD This is the file used to load the "SMP" driver which in turn is used for sampling sounds via the microphone of the Psion 3A and storing the sampled values directly to memory. It is an experimental product from Psion and is not currently supported. No claims can be made as to its stability. It may reset or crash your machine or cause data loss. (I have used it for some time without any adverse effects). USE The following procedure will allow you to test the DTMF tones produced by your 3A: 1. Change the duration of DTMF tones to 2 seconds using PSION-SHIFT-D from the system screen and changing the tone time parameter to 64. 2. Open a data file and use the free dial option to generate a DTMF tone (ie dial a digit !) and record this using a dictaphone or a tape recorder. 3. Close the data file and open the DTMFTEST application. Bypass the first few screens and load the SMP driver. At this stage you will get the "Press a key to sample DTMF tone" message. Now play back the tone you recorded and with the Psion microphone close to the recorder's speaker press a key. You will have to wait approximately 1.5 minutes for the results of the tests. (The program uses a fast fourier transform but "fast" is a relative term !). Pressing a key after the results are displayed will delete the SMP driver from memory. You may exit at this stage or load the driver and run the test again. If you exit the application using some method other than that presented by the program, the SMP driver will stay loaded in memory (using about 6K ). To delete the driver, simply run the application again and press ESC to exit at the appropriate screen. DISTRIBUTION You are free to distribute this program providing this textfile is distributed with it. However, the following exception applies: << You may not distribute this program via "Premium Rate" bulletin boards. >> No charge may be levied for this product. CONDITIONS of USE: This program is used entirely at your own risk. Reverse engineering is not allowed. It may not be used commercially. Please send comments and bug reports to : djoyce@cix.compulink.co.uk or djoyce@telecom.ie end of text file