Abstract: A Precision Approach Path Indicator (PAPI) unit comprises first and second light sources and a projection lens assembly. Light emitted by the first and second light sources is collected by first and second solid waveguides respectively and is guided by said waveguides to an intermediate plane. The intermediate plane is located in the focal plane of the projection lens assembly.

Abstract: Coin validation apparatus may be associated with a coin freed mechanism on coin receiving machines or form part of a coin sorting apparatus to check that coins are valid coins and not counterfeit. Recently, it has become particularly convenient to use the interaction between a coin and an alternating magnetic field to gauge various parameters of the coin thereby to determine if the coin is valid. In such a method the frequency of a feedback oscillator having a tuned electrical coil in its feedback loop is monitored when a coin is present adjacent the coil, the frequency is then monitored when a phase shift or time delay network is also included in its feedback loop, two parameter signals characteristic of the effect of the coin on both the inductance and the loss factor of the coil, are derived from these maintained frequencies and the two parameter signals are compared with reference values to determine if the coin is valid.