Resistors Rl and R2 temperature-stabilize the NAND gates; they also ensure that the gates are in a linear region for starting. Capacitor CI is a dc block; it must have less than Vw ohm impedance at the operating frequency. The crystal runs in a series-resonant mode. Its series resistance must be low; AT-cut crystals for the 1- to 10-MHz range work well. The output waveshape has nearly a 50% duty cycle, with chip-limited rise times.