NDC 96 is the name of a series of ministep bipolar chopper drives, suitable for driving two-phase stepping motors, with four, six or eight terminals. NDC 94 and NDC 96 series drives are housed in a metallic box, 110 x 108 x 34 mm format suitable for wall mounting, by means of screws or mounting brackets separately supplied by R.T.A. as an option. They require a single DC supply voltage and do not need external fans: accordingly they are ideal both for mounting inside a metallic electrical cabinet and for stand-alone applications. Optoinsulated and differential input and output signals ease interfacing with the most commonly used control systems and ensure high noise immunity. The ministep operation, connected with a further electronic resonance damping facility, ensures excellent operating smoothness and low acoustic noise. R.T.A. experience, together with a careful design for these specific purposes, has led to a high reliability component, in spite of its very competitive cost.unity.