difference between sinusoidal & relaxation oscillator?

In nature many oscillations are Sinusoidal including the oscillations of current between an Inductor (L) and Condenser or Capacitor (C), connected in parallel. Part of the current is fed back in positive phase in an Amplifier configuration to produce sustained oscillations. This is the earliest general design of Sinusoidal Oscillators.

Later a back-to-back amplifier configuration was tried with two active devices(tubes or valves initially and later with transistors). In this each amplifier feeds into the other which in turn feeds it to the first, thus setting up sustained oscillations with a Capacitor to get charged and after a certain period release into the input of the other stage. It is a switching configuration in which one gets saturated fully, while the other is 'off ' (no current almost). The charging and relaxation of Capacitor depends on the time constant ('RC') of it and the resistance through which it discharges. Charge-relaxation cycle of one stage's Capacitor is in reverse order with the other of the other stage. The switchover thus is free running and instead of Sinusoidal waveform ('Current' versus time). Relaxation oscillator was first used in conjunction with invention of Radar for 'timing' the Magnetrons (used in Microwave ovens now). {Why did you not post it in Engineering section?}

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