Crab´s-eye filter Novel synthesis procedure for sets of band-separation filters

There are many applications in communication and instrumentation which require a bank of bandpass filters with adjacent passbands, such as telephone tone-signalling systems, Doppler-radar systems and speech-analysis systems. By use of the technique of crossconnected feedback, these may be realised using a lower average number of critical components per filter channel than by existing procedures. The paper discusses the basic system and its analysis, and outlines some of the design procedures. There is also a discussion of the sensitivity of the system to component values. Some details are given of the practical application of this system to the tone receiver for use with pushbutton telephones. The name arises since the system was developed by analogy to the biological principle of lateral inhibition in the optical system of the Limulus crab.