The paper discusses progress on the topic of wave filters realised by a variety of approaches in digital technology and presents, in summary, an introduction to relevant theoretical concepts. The implementation of these filters is dependent on the efficient realisation of elements known as adaptors. This paper describes a universal adaptor concept which allows the realisation of either series or parallel adaptors. The Edinburgh FIRST silicon compiler has been used to design the universal adaptor structures, and example circuit layouts are given, in 5 μm NMOS technology, of filters with common frequency-selective characteristics. The future potential of the wave-filter approach to digital filtering is discussed, particularly with reference to CMOS integration.