Patent ID: 6097796
Filing Date: 2000-08-01
Classification: H04N

Abstract:
A communications terminal apparatus, comprising:a data transmitter and receiver;memory for storing first and second reference time ranges;a tone detecting filter for detecting a signal tone on a telephone line;an energy detecting filter for detecting an energy on the telephone line;a first timer for measuring a tone state time period of a signal on the telephone line;a second timer for measuring an off-tone state time period of said signal; anda busy tone detector for determining whether said measured tone and off-tone state time periods of said signal are within said first and second reference time ranges, respectively, and whether said signal alternately includes said measured tone and off-tone time periods, and for determining that said signal includes a busy tone when said measured tone and off-tone state time periods of said signal are within said first and second reference time ranges, respectively, and when said signal alternately includes said measured tone and off-tone time periods, wherein the busy tone detector is capable of determining a busy tone using an output of the tone detecting filter and the energy detecting filter, the busy tone being determined when a busy tone is detected from the output of the tone detecting filter or the energy tone detecting filter.