Sound deviation measuring appts - delivers voltage corresponding to frequency variations using phase comparison stage and LF generator

摘要

A low pass filter (2) is connected to a phase comparison stage (1), an amplifying stage (3) following. the output of this stage (3) feeds simultaneously a measuring instrument (4) and a regulating lead (5). The latter (5) connects the amplifying stage (3) with a low frequency generator (6) whose frequency can be controlled. The frequency regulating circuit is completed by the connection of the generator output with the comparison stage (1). The latter (1) comprises a transistor (7), an emitter voltage divider (8) and a collector voltage divider (9). The generator is so adjusted that it oscillates at the test frequency when it receives no signal from the control line (5).