The paper covers the salient features, comparisons and potential of recent developments in analogue signal processing hardware: surface-acoustic-wave (SAW) devices, charge-transfer devices (CTD), and also switched-capacitor filter networks. After describing the operating principles of these devices, their potential for several important signal processing roles is reviewed. Applications are treated where the performance capabilities of the devices overlap. Recent developments in optical and acousto-optical signal processors are reviewed and their future potential is examined. Finally, SAW and CTD performances are compared with available very large-scale integration (VLSI), and the potential of VLSI hardware for digital signal processing (DSP) is discussed.