Improvements in or relating to electronic computing equipment

833,006. Attenuation/frequency measurements; phase - frequency measurements. BRITISH TELECOMMUNICATIONS RESEARCH Ltd. Jan. 13, 1958 [Jan. 14, 1957], No. 1385/57. Class 37. Equipment, particularly for designing electrical networks, in which the coefficients of the terms of a convergent series expansion of an arbitrary response function representing the desired characteristics of a network and similar coefficients derived from the series expansion of the actual response function of a trial network are compared, comprising a digital computer for calculating the differences between corresponding coefficients, each said difference controlling the 'output from a corresponding source of sinusoidal voltage, said sources being related harmonically; the outputs being combined in an adder and applied to the Y-plates of a cathode-ray oscilloscope, a voltage of the fundamental frequency being applied to the X-plates, the display giving an indication of the differences of the trial network from the desired characteristics. In the particular embodiment, attenuators AA1-AA4 and PA1-PA4 energized from a constant zero-frequency signal and oscillator O are respectively controlled by the differences calculated by the computer, the constant signal, even harmonics, attenuators AA1-AA4, adder AA and oscilloscope AT providing the amplitude difference display and attenuators PA1- PA4, the odd harmonics, adders PA and oscilloscope PT the phase difference display Lissajous figures are produced on the oscilloscopes and the parameters of the trial network adjusted until the figures become straight lines when the differences between the trial network and the desired characteristic are zero. A Tchebeychev expansion of the logarithm of the response function is used. The control of the attenuators may be effected in steps by relays, or, if the attenuators are replaced by amplifiers, the information from the computer may be converted into a voltage which is used to control the gain of the respective amplifier.