METHOD AND CIRCUITRY FOR CONTROLLING VOICE MAIL, CALL LOGGING AND CALL BLOCKING FUNCTIONS USING A MODEM

摘要

A telephone line monitoring circuit (100) for a MODEM monitors the TIP and R ING lines (106, 108) of the telephone line. A first circuit (110) detects when a local phone goes off-hook while the MODEM is on-hook by sensing a decrease in a differential volt age between the TIP and RING lines (106, 08). A second circuit (120) detects the pick up of a local phone while the MODEM is off-hook by detecting a change in the impedance between the TIP and RING lines (106, 108). A third circuit (120) detects the hang up of a rem ote phone connected with the MODEM while the MODEM is off-hook by detecting a te mporary break in the DC loop between the central office and MODEM. A snoop circuit (130) monitors the telephone line for DTMF signals while the MODEM is on-hook.