Even though cordless phones have invaded our homes and offices, you don’t always have them at hand, and as their ringtones are usually very much quieter than the old rotarydial- type analog... Read more
If you are lucky enough to have a big house, a large garden, and small children, this project just might interest you. It’s actually a telephone ringer capable of making any mains-powered de... Read more
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
Circuits have been published on earlier occasions that keep an eye on the telephone line. This simple circuit does it with very few components and is completely passive. The operating princi... Read more
Generated millions of times every day by our telephone keypads, the eight DTMF frequencies were chosen so that the harmonics and intermodulation do not generate significant in-band signal le... Read more
The circuit depicted here forms one half of a device that will prove extremely handy when tracing the path of electrical wiring in a building or to locate a break in a wire. The system is ba... Read more
It is sometimes necessary to make a telephone conversation audible to more than one person at either end or to make a tape recording of it (as in many businesses). Often, this is done with t... Read more
Undesired listening-in to phone conversations may be prevented by the present circuit, which requires only two components to protect a telephone. In each telephone to be protected, a traic i... Read more
Since in some countries, it may be illegal to connect the circuit to the public telephone network, to check with your local telephone manager before building this circuit. In most telephone... Read more
The modern telephone can easily be connected in parallel, enabling a household to have one in the bedroom, kitchen and hall or study. It is, however, not always easy to see (or hear) at one... Read more
