The ABLS-4.000MHZ-K4T is an HC/49US (AT49) SMD low-profile crystal oscillator designed for precision frequency control applications. Operating at a fundamental frequency of 4.000 MHz with an equivalent series resistance (ESR) of 180 O maximum, this crystal features a compact form factor of 11.5 × 4.7 × 4.2 mm and is RoHS compliant with hermetic sealing for moisture protection. The device operates over an extended temperature range of -40°C to +125°C with frequency tolerance of ±50 ppm at +25°C and frequency stability of ±50 ppm over the operating temperature range. Key electrical characteristics include a shunt capacitance of 7 pF maximum, load capacitance of 18 pF, and drive level of 1 mW maximum (100 µW typical), with aging of ±5 ppm maximum in the first year. This crystal is ideal for computers, modems, microprocessors, and wireless applications requiring stable frequency references with reliable performance across demanding temperature environments.