This paper presents the outcomes of laboratory testing on a sample of LED lamp/driver and dimmer combinations in presence of Audio Frequency Injection Control (AFIC) signals used by network operators for control of certain loads. In order to determine contributing factors in the signal that may have an effect on the performance of the LEDs, a flicker evaluation testing system has been developed to investigate flicker issues associated with LEDs under controlled conditions. The main objective is to use light based flicker indices to identify the effect on different lighting combinations by varying the voltage magnitude, frequency of the AFIC signal and the position of the dimmer. Visual observations were also carried out to ensure that results obtained from the testing are correlated with what was observed visually. The test results have been analyzed in terms of types of technologies used in LED lamp/driver and the variables in the AFIC signal, and analytical results are reported in the paper.