Frequenzmessung mit Multimeter (f/U-Wandler 4151, 10 Hz-10 kHz)

Another project for which a free printed circuit board is being offered, this cir- cuit was first featured in the July/ August 1977 issue, but for readers who missed that issue a short resume of the project is given here. The `knotted handkerchief`, as its name implies, is a circuit that reminds one to do something; in fact, it is an extremely compact timer and alarm that can be carried in a pocket. The heart of the cir- cuit is an oscillator and 14-stage binary counter, IC