This circuit is from old documentation, but it can be implemented with modern transistors such as 2N2222 for bipolar and BF124 for FET. The crystal determines the operating frequency.
Combining an Ultra-Low Power MCU with an 802.15.4 Radio, the SAM R30 Enables Long-Lasting Battery...
This comparator with two Texas Instruments operators was obtained in a company application manual....
August 2017 - Mouser Electronics already has the Connect One Pico WiReach ™ SMTS Pico modules...