Finite automata, regarded as sequence transducers or encoders, are good models for analyzing characteristics of transmission codes. From such a stand point, some properties of transmission codes have been examined and some results obtained. First, the necessary and sufficient condition for a transmission code to have power spectral null at frequency f(h/k)f_r is obtained, where h and k are relatively prime integers and f_r is the pulse repetition frequency. It would be the most general result in the problem of power spectral nulls, although the special case where h/k0/1 is already known. Such a code is inherently modulating and, therefore, matches specific requirements in transmission system design. Second, it has been shown that spectral transformation is possible only by restricting inputs appropriately. In particular, it is illustrated that various transmission codes with dc-component can be made dc-component free by appropriately restricting inputs.

Lasing modes of the TJS-lasers (transverse-junction-stripe lasers) have been examined. Typical near and far field patterns show the fundamental transverse mode both in the x and y directions. From these patterns, the refractive index difference between the active region and the p-GaAs region is estimated to be about 0.2%, and that between the active region and the n-GaAs region to be 0.5-1%. Using these values, it is shown that only the fundamental transverse mode can propagate in the active region. The lasing spectra show a nearly single longitudinal mode operation in a wide range of the input current. The transition behavior of the longitudinal mode has been examined experimentally, and it is suggested that the single mode operation is caused by a heavy doping profile in the active region.

A method of realizing a gyrator is presented. In this circuit, we can easily adjust the Y-parameters of the gyrator, Y₁₁, Y₁₂, Y₂₁ and Y₂₂, independently.A simple application of the gyrator to all-pass network is also given.

This paper describes the new type Solion Triode whose electrode gap is controlled by the electrodeposited (or electrodissolved) metal on (or from) one electrode of the two.