TTL crystal oscillator

A quartz crystal oscillator is formed by connecting a quartz crystal in series with a coupling capacitor in a symmetrical multivibrator. The oscillation frequency of the circuit depends on the resonant frequency of the quartz crystal, which is related to the absence of R and C in the circuit. Figure b is the circuit of figure a The coupling capacitor in is replaced by a coupling resistor. Figures c and d are deformations of figures a and b, which are also two practical circuits.