I was surprised to see, today, one of my photos on the cover of a book: Practical Electronics Handbook (6th Edition). The authors didn't need to ask me for permission, as I had previously sold the copyright to Wimborne Publishing. It is a photo of one of my constructional projects, called the Multi-Clap Switch. I could have used a microcontroller for this, but I used logic chips, because logic chips are forever. A clap switch will typically turn on a light with a clap, or a clap-clap. Mine, however, accepted between one and ten claps, at any preferred tempo, with the possibility of removing claps from the sequence. OBSERVATION: This potentially made it a security device. To copy, say, a clap-clap-stop-clap at a precise tempo is very difficult.