Modulation voltage level difference measuring cct. - has sensitivity level independent of voltage scale

摘要

The circuit has two identical input channels each comprising an input amplifier and a rectifier circuit which generate two d.c. voltages of the same polarity from the two modulation voltages and feed to an electronic switch for alternate scanning and transmission. To measure the level difference between the two modulation voltages, a logarithm generating stage pref. with a control stage is connected directly to the switch. The advantage of the invention is not so much that apparatus for the production of the second logarithmic characteristic can be spared, but rather that the high specifications necessary for the accurate parity of two log characteristics are not required. It is sufficient to produce a single, chosen, log characteristic.