The HY-03DTD is a dial tone detect add-on board for the HY-03 range of products. As standard, the HY-03 range can automatically disconnect the line once K-break is sensed. Using the HY-03DTD allows automatic disconnection in different countries based on the following table: Country or Equipment Type Frequencies Type Details Austria 440Hz Continuous – Avaya PBX 400Hz Cadence 375ms on, 375ms pause Belgium 450Hz Continuous – Bulgaria 425Hz Cadence 250ms on, 750ms pause, 750ms on, 1000ms pause Cyprus 350Hz and 450Hz Continuous – Czech Republic 425Hz Continuous – Denmark 425Hz Continuous – Finland 425Hz Continuous – France 440Hz Continuous – Germany 425Hz Continuous – Greece 440Hz Continuous – Hungary 440Hz Continuous – Iceland 425Hz Continuous – India 400Hz Cadence 750ms on, 750ms pause Ireland 400Hz and 450Hz Continuous – Israel 400Hz Continuous – Italy 425Hz Cadence 200ms on, 200ms pause, 600ms on, 1000ms pause Italy2 425Hz Cadence 200ms on, 200ms pause Japan 400Hz Continuous – Luxembourg 425Hz Continuous – Netherlands 450Hz Continuous – Norway 425Hz Continuous – Poland 425Hz Continuous – Portugal 425Hz Continuous – South Korea 350Hz and 440Hz Continuous – Spain 425Hz Continuous – Sweden 425Hz Continuous – Switzerland 425Hz Continuous – Taiwan 350Hz and 440Hz Continuous – United Kingdom 350Hz and 440Hz Continuous & Cadence 750ms on, 750ms pause United States 440Hz and 480Hz Continuous