The ECS-36-18-4X is an HC-49USX low-profile resistance weld type through-hole quartz crystal designed for cost-effective timing applications. It operates across a frequency range of 3.57 to 70 MHz with fundamental mode operation up to 30 MHz and 3rd overtone mode from 27 to 70 MHz, offering flexible frequency selection for diverse circuit requirements. The crystal features a maximum frequency tolerance of ±30 ppm at +25°C and frequency stability of ±50 ppm over the operating temperature range of -10°C to +70°C, with a shunt capacitance of 7 pF and load capacitance options of 10 or 20 pF. The device is RoHS compliant, Pb-free, and rated MSL 1, with a maximum drive level of 500 µW, making it suitable for consumer electronics, communication systems, and industrial timing applications where reliable frequency control and compact form factor are essential.