This paper discusses the problems arising in the realization of practical, wide-band signal correlation systems and presents some possible solutions to these difficulties. Function generators and shift-register encoders in particular solve the problem of long, stable delays, by providing wide-band signals that can be reproduced accurately with any desired time delay or Doppler compensation. The use of clipped signals permits operation over a wide range of input-signal amplitudes, while sacrificing absolute amplitude information and some processing gain. High search rates and processing real time are achieved with multichannel correlators, compressed-time correlators, and matched filters. Several ways of instrumenting digital delay-line time compressors, digital-scanned-storage time compressors, and digital matched filters are discussed, including their integration into real-time processing systems. The relative advantages of the different approaches are discussed.