Method and circuitry for controlling voice mail, call logging and call blocking functions using a modem

A snoop circuit for a MODEM that monitors a telephone line for DTMF signals without putting a DC load on said telephone line, and that generates an output signal representative of said DTMF signals on said telephone line, comprising:

• a first input connected to a TIP line of said telephone line;
• a second input connected to a RING line of said telephone line;
• a DC current blocking element for preventing a DC current from flowing through said first input and said second input, said current limiting element thereby allowing said MODEM to monitor said telephone line while on-hook;
• and
• means for reproducing said DTMF signals on said telephone line as said output signal.

A method of using a MODEM having a snoop circuit to monitor a telephone line while said MODEM is on-hook, and to record information regarding incoming and outgoing calls monitored by said snoop circuit, said telephone line having a TIP line and a RING line, said method comprising the steps of:

• detecting a ring signal on said TIP line and said RING line of said telephone line;
• detecting a caller ID signal transmitted on said TIP line and said RING line during said ring signal using said snoop circuit;
• decoding said caller ID signal to produce a telephone number that represents an incoming call;
• recording said telephone number that represents said incoming call;
• recording a time indicating when said incoming call was received;
• detecting when a local phone is off-hook by sensing a voltage drop occurring across said TIP line and said RING line when said local phone goes off-hook;
• monitoring said TIP and said RING line using said snoop circuit while said local phone is off-hook to obtain a telephone number that represents an outgoing call;
• recording said telephone number that represents said outgoing call;
• and
• recording a time indicating when said outgoing call was placed.

A telephone line monitoring circuit for a MODEM, said monitoring circuit comprising:

• a first input connected to a TIP line of a telephone line;
• a second input connected to a RING line of said telephone line;
• a first circuit that detects when a local phone goes off-hook while said MODEM is on-hook by sensing a decrease in a differential voltage between said TIP line and said RING line occurring when said local phone goes off-hook, said first circuit providing a local off-hook output signal responsive to said decrease in said differential voltage;
• a second circuit that detects a local pick up while said MODEM is off-hook by sensing a change in an impedance between said TIP line and said RING line occurring when a local phone goes off-hook while said MODEM is off-hook, said second circuit providing a local pick up output signal responsive to said local pick up;
• a third circuit for detecting a remote hang up when said MODEM is off-hook by sensing a decrease in said differential voltage to substantially zero occurring when a central office temporarily turns off a DC current loop to said MODEM in response to said remote hang up, said second circuit providing a remote hang up output signal responsive to said remote hang up;
• and
• a snoop circuit that monitors said telephone line for DTMF signals while said MODEM is on-hook, said snoop circuit being AC coupled to said telephone line such that no DC load is placed on the telephone line, said snoop circuit providing an output signal representing said DTMF signals on said telephone line.

A telephone line monitoring system for allowing a computer to monitor both incoming and outgoing telephone calls without going off-hook, and to generate a record of the incoming and the outgoing telephone calls, comprising:

• a MODEM connected to said computer;
• a snoop circuit on said MODEM and connected to a telephone line, said snoop circuit providing an output signal representing signals on said telephone line, said output signal provided to decoding circuitry of said MODEM, said snoop circuit including coupling circuitry for preventing a DC load from being placed on said telephone line, said coupling circuitry thereby allowing said MODEM to monitor said telephone line while on-hook;
• and
• a software module which runs on said computer, said software module configured to, while said MODEM is on-hook, do each of:
• (a) monitor an on-hook/off-hook status of a local phone, and (b) when said local phone is off-hook, record a telephone number of an outgoing call placed from said local phone, said telephone number captured via said snoop circuit.

A method of using a MODEM to selectively block calls placed from a local phone, said MODEM and said local phone connected to a common telephone line, said method comprising the steps of:

• detecting when said local phone is off hook;
• monitoring tones on said telephone line while said local phone is off hook to detect a telephone number of an outgoing call placed from said local phone, said step of monitoring performed without placing a DC load on said telephone line so that said MODEM remains on hook;
• comparing said telephone number to at least one predetermined number;
• and
• blocking said outgoing call when said telephone number matches said predetermined number.