pad, being sure to use the proper signs (+ or -). Press the "2nd" button; then press the "log" button. After a short processing interval, the equivalent number is shown on the display. Let us get to the crux of the matter. We are interested in dBs. Let us suppose we are given 13 dB and we are asked to find its numeric equivalent (power domain). This calculation is expressed by the following formula: log-1(31/10)=20. LEARNING DECIBELS AND THEIR APPLICATIONS Let us use a calculator and compute the following equivalent numeric values when given dB values: 1. -21.5 dB. Divide by 10 and we have -2.15. Enter this on the keyboard with the negative sign. Press 2nd F (function) to access the upper case, which is the same as the log button but marked right above "10x." Press = button and the value 0.00708 appears on the display. 2. +26.8 dB. Enter this number on the keypad and divide by 10; press = Press 2nd F; press log button (10x) and press = The equivalent numeric value appears on the display. It is 478.63. When working in the voltage or current domain, we divide the dB value by 20 rather than 10. Remember we are carrying out the reverse process that we used calculating a dB value when given a number (numeric) (i.e., the result of dividing the two numbers making up the ratio). This is expressed by the following formula: log-1 (dB value/20) = equivalent numeric. Consider this example. Convert 26 dB (voltage domain) to its equivalent numeric value. Enter 26 on the keypad and divide by 20. The result is 1.3. Press 2nd F button and press the log button (10x) and press = The value 19.952 appears on the display. The reader probably did this in his or her head and arrived at a value of 20. Try the following six example problems, first in the power domain, and then in the voltage/amperage domain. The correct answers appear just below. 1. -6 dB 2. +66 dB 3. -22 dB 4. +17 dB 5. -27 dB 6. +8.7 dB Answers: 1: 0.251; 0.501. 2: 3,981,071.7; 1995.26. 3: 0.006309; 0.07943. 4: 50.118; 7.07945. 5: 0.001995; 0.044668. 6: 7.413; 2.7227. C