The XC2151 series are a group of high frequency, CMOS low power crystal oscillators with oscillator & divider circuitry, oscillator capacitors and amplifier feedback resistors built-in. An oscillator circuit can be created from just an external crystal. Output frequency can be selected from four frequencies : Fundamental f0/1, Divided f0/2, f0/4, f0/8. The output buffer is 3-State and has a fanout of 10 - TTL.