system circuit 22 fig1 the cathode of a diode 190 and the anode of a diode 192 are connected together and to the output of the operational amplifier 186 the anode of a diode 194 and the cathode of a diode 196 are connected together and to ground the cathode of the diode 192 and the anode of the diode 196 are connected together and to the cathode of the light emitting diode 176 of the photoconductive module 172 the anode of the diode 190 and the cathode of the diode 194 are connected together to the first side of a resistor 198 and to the anode of a diode 200 the second side of the resistor 198 and the cathode of the diode 200 are connected together and to the anode of the light emitting diode 176 of the photoconductive module 172 in the preferred embodiment the resistor 198 has a value of 1k ohms and the diodes 190 192 194 196 and 200 are all standard value diodes this completes the description of components in the limiters 62 64 66 68 70 72 74 and 76 referring next to fig5 the electrical schematic of the active combining network 94 used in the first channel accurate reproduction system circuit 22 of fig1 is illustrated the.