By using the optional Audio Input Module (LJ Order code CT7) and the Audio Output Module (LJ Order code CT8), we can use voice signals as the audio modulating signal instead of the ANACOM 2's Audio oscillator. If you have these modules, make the same connections as in Practical Exercise 8.4. When you have finished, switch off the power supply and disconnect all leads from the Audio Input and Audio Output modules. Except for the power supply connections, remove all the other connections from the ANACOM 2 board. 8.8b The Quadrature Detector: Lal has less of a problem with noise than does the Detuned Resonant Circuit Detector. b uses a phase comparator and is therefore able to receive both AM and FM signals equally well. Lc can only eliminate noise frequencies around 2kHz owing to the low pass filter used. ld is less able to eliminate noise than is the Detuned Resonant Circuit Detector. We will now perform a similar investigation into the operation of the PLL Detector. Just before we start, ensure that on the ANACOM 2 board, the following initial conditions are set: a) All the switched faults set to oFF. b) FREQUENCY preset in the Audio oscillator block set to minimum (fully counter-clockwise). c) AMPLITUDE preset in the Audio Oscillator block set to maximum (fully clockwise). d) AMPLITUDE preset in the MixerIAmplifier block set to maximum (fully clockwise). e) VCO switch in the PLL Detector block set to ON. Switch on the power supply.