Abstract: A method of self-diagnosis in a digital signal processing system. The digital signal processing system comprises a digital signal processing apparatus which includes a plurality of electronic components for processing signals in a plurality of channels. An output of the digital signal processing apparatus is coupled to an input of the digital signal processing apparatus. A central processing unit causes one after another of the electronic components to generate a predetermined signal while the other electronic parts are in a condition for passing the predetermined signal therethrough. The CPU then checks whether or not the output of the digital signal processing apparatus is correct. When the output of the digital signal processing apparatus is not correct, the central processing unit outputs a unique reference number for the electronic component from which the predetermined signal was then generated. The reference number for the electronic component is visually indicated on a bar graph meter.

Abstract: In this digital signal measurement apparatus, an approach is employed to deliver a measurement signal from a measurement signal generator to a measured circuit to transform the signal on the time base through the measured circuit to a signal on the frequency base by a frequency base transform circuit and to further obtain a signal on the time base by a time base transform circuit. Thus, a difference between the signal on the time base through the measured circuit and the signal on the time base from the time base transform circuit is employed. Thus, for example, even if the measured circuit is a linear system, a measured result in the digital region and a result of the analog measurement can be in correspondence with each other. Accordingly, gain correction of a measurement signal is unnecessary, thus making it possible to prevent an increase in an error of a measured result of S/N.

Abstract: A portable data terminal unit includes a data RAM for storing transaction data, and an acoustic coupler for transmitting the data stored in the data RAM to a computer installed in a business office. The portable data terminal unit has a battery for power supply purposes. The acoustic coupler is connected to the battery at a desired time for data transmission purposes. The data RAM is continuously connected to the battery for maintaining the transaction data stored in the data RAM. The present portable data terminal unit is suited for money collecting operations related to the insurance business and the installment savings business.