PLL is a linear phase-locked loop control system analysis program, useful for analyzing and or predicting the behaviour of a given phase-locked loop. PLL is capable of calculating open and closed loop gain (magnitude), open loop phase and error responses as a function of frequency, the closed loop transient (time domain) response for a given input excitation and the closed loop SSB phase noise spectral density for the given system. The program includes a built-in graphics capability and operates on pull down menu system.