After the Great War, the United States and England are more widely developing the Printing Telegraph system. This paper concerns such latest machines. First, the various kinds of printers are discussed and 5-unit code is compared with Morse code and it is proved that the former is the best type of signal from the standpoint of line economy. Next follow the full details of Western Electric Multiplex Printer, Start Stop Printer, Kleinschmidt Printer, and Teletype. Finally, the advantages and disadva-ntages of various printers are compared and the author's views on the design of printers for the Japanese characters are given.

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When a plunger type relay is so connected in an electric circuit as to guard against over load, it is sometimes observed that the plunger is first pulled up by the sudden increase of the load current, but even if this over load current is maintained the plunger happens to drop. The caurse of this phenomenon might seem to be:
1. The counter e. m. f. induced in the solenoid due to the sudden motion of the plunger; it is however, experimentally affirmed that the pull does notldecrease by its movement, and hence the counter e. m. f. is probably not the chief caurse.
2. The upward motion of the plunger is to increase the inductance in the secondary circuit of the current transformer. It is theoritically proved that corresponding increase of the primary voltage, and consequently the magnetizing current, might bring about the said disturbauce. That either of these is not the true cause can be understood from the theoretical conclusion, that, so long as the secondary voltage is constant, the magnetic pull does not decrease owing to the plunger motion.
3. The increase of the iron loss in the relay may also be a cause of the phenomenon.
How the magnitude of the pull varies with the initial position of the plunger is then experimentally determined, from which it can be infered, that, in order to prevent this disturbing phenomenon, the initial position of the plunger i. e. the initial length of the air gap must be properly selected.
Many informative results have subsequently been obtained about the performace of a plunger type relay by experimentally determining the velocity and the dynamic pull at every point of the travel during the upward motion of the plunger.

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