This paper proposed two models of a periodically time-varying digital filter. One model is similar to a polyphase digital filter (polyphase model) and the other a coefficient-varying model. These models are different essentially. However, it was proved that under certain conditions, filters described by the coefficient-varying model is equal to the polyphase model. Moreover, it was shown that the relationship between the power of an input signal and of an output signal in a periodically time-varying digital filter, which correspond to the well-known Manly-Row law in an analog time-varying circuit was derived.

This paper presents a method of implementing a signal source needed in a subtractive digital musical synthesizer. In this proposed method, the basic source is ROM containing 12 signals for one octave. Signals for lower octaves are obtained by using interpolation, and signals for higher octaves by decimation, Moreover, signals which are composed of spectra difficult to generate by analog methods can be generated easily.

One of the synchronized systems of large digital transmission networks is the mutually synchronized system called the equational timing system. This system is, however, complicated, and its dynamic responses are not obtained analytically for general configuration. This paper describes dynamic responses and stability conditions of mutually synchronized systems applying the equational timing system under less stringent restrictions compared with previous discussions. Similar results for the fundamental mutually synchronized system can be obtained easily.