Many ‘busy’ indicators for use in telephone systems present undesirable loading of the telephone line. Some circuits are very simple indeed to the extent of only loading the line when it is... Read more
Here is a simple 10-watt audio amplifier using IC LM1875. The IC has five pins and can deliver a maximum of 18-watt output power depending upon the supply voltage and load. The author’s prot... Read more
When turning a computer on and off, various peripherals (such as printers, screen, scanner, etc.) often have to be turned on and off as well. By using the 5-V supply voltage from the USB int... Read more
When the environment is hot in the heat sensitive circuit, the voltage on the NTC decreases. T2 switches to cut, T1 switches to transmission. Relay contacts change position. When the environ... Read more
Integrated circuits ISD 1012, ISD 1016 and ISD 1020 from chip maker ISD enable sounds to be recorded and played back. The final two digits in type coding show the length of a sound message i... Read more
