  We have presented an unified scheme to express a class of system of equations
in two variables into a Li\'enard-Levinson-Smith (LLS) oscillator form. We have
derived the condition for limit cycle with special reference to Rayleigh and
Li\'enard systems for arbitrary polynomial functions of damping and restoring
force. Krylov-Boguliubov (K-B) method is implemented to determine the maximum
number of limit cycles admissible for a LLS oscillator atleast in the weak
damping limit. Scheme is illustrated by a number of model systems with single
cycle as well as the multiple cycle cases.
