Cal Triangle provides a complete external exchange station (FXS) single-channel telephone interface solution, compliant with all relevant global standards. Compared to other competitors in the industry, the device is designed to use a capacitive boost tracking negative power supply, featuring low power consumption, low cost, and small area. Self-diagnosis and loop testing (MLT) are achieved through built-in DSP, monitoring ADC, and test load, providing better audio quality and DTMF (Dual Tone Multi Frequency) detection than PSTN (Public Switched Telephone Network).