This disclosure relates to signal level control instruments for sound transmission systems comprising a signal top value measuring instrument for indicating a maximal reference volume for a high quality sound signal transmission in the system without exceeding a desired maximum distortion of the signal and, in particular, transient signals of short duration. The invention teaches the use in combination with a signal top value measuring instrument of a weighing network inserted between the top value measuring instrument and the transmission chain, the output signal of which is to be measured, said weighing network having an attenuation function being essentially an image function of a function defining the maximum input signal level versus frequency for a predetermined relative intermodulation distortion. This function is obtainable for a particular signal transmission chain by aid of conventional intermodulation measuring instruments in accordance with CCIF standard, for instance, and is in the following referred to as tolerance characteristic of the transmission chain.
The present invention relates to an apparatus for measuring the level of a signal voltage supplied to the control input of a controllable constant current source whose output is connected to a phase inverting circuit conducting in one direction and to a rectifier conducting in the opposite direction so that a full-wave rectified current is obtained which is adapted to flow through a measurement device in order to obtain a measure of the voltage level.
A peak voltage detector responsive to a wide band AC signal, which detects both the negative and positive peaks of the signal, indicating which is the larger. The signal is applied to a transistor amplifier, and outputs are taken from equal collector and emitter loads through capacitors and diodes to a common high resistance load and a sustain timing capacitor in parallel to the load. The voltage across the latter is applied to the base of an emitter loaded Darlington amplifier. The emitter load includes a meter in series with a second time constant circuit. The function of the second time constant circuit is to accelerate upward deflection of the meter. The function of the first time constant circuit is to hold a charge long enough to maintain the meter reading for a time after the peak pulse has passed.
