pseudo PROM

Most people wilt have seen the desk-top ornament/toy known as a `Newtons cradle` (see figure 1), which consists of usually five steel balls suspended in a row frol`T` a pair of threads. When one of the end balls is lifted and then released so that it falls back and strikes the next ball, the energy of the impact is trans-mitted through the other balls, with the result that the ball on the opposite end of the row swings up. It then in turn falls back, energy is again transmitted through the row, and the first ball swings up, and so on. The energy losses of the system are fairly high, and after a number of oscillations the balls are returned to rest. The idea behind the circuit described here, is to compensate for the natural energy losses of the system, so that it continues to oscillate indefinitely (i.e . until the circuit is disconnected or the bat-teries run out!).