Security apparatus and method for computers connected to telephone circuits

A method of protecting a computer system connected into a telephone circuit from unauthorized calls, said method comprising the steps of:

• answering through a first modem an incoming call before the call is received by the computer system, which incoming call is initiated from a calling end and transmitted over the telephone circuit to the first modem;
• detecting whether a predetermined event occurs after the incoming call is answered by the first modem;
• and
• transferring through a second modem the incoming call to the computer system only if the predetermined event occurs and is detected so that communication between the computer system and the telephone circuit occurs through both of the first and second modems.

A system for connecting a computer with an incoming call over a telephone circuit, said system comprising:

• a first modem connected to said telephone circuit for answering said incoming call without emitting an audible carrier tone;
• a second modem connected to said computer;
• controller means, connected to said first modem and said second modem, for controlling said second modem in response to a valid incoming call being received through said first modem so that said computer is communicated through both said second modem and said first modem to said telephone circuit to receive said valid incoming call, said controller means comprising:
• timer means for detecting the expiration of a predetermined timing period commenced in response to said first modem answering said incoming call, said timer means generating a time signal indicating that said timing period has expired, and
• a modem ring circuit, responsive to said time signal, which generates an internal call to said second modem upon receiving said time signal so that, upon answering said internal call, said second modem and said computer are in communication with said telephone circuit through said first modem;
• and
• means, connected between said computer and said first and second modems, for disconnecting said modems from said valid incoming call when said first modem, said second modem, and said computer are all in communication with said telephone circuit and an incorrect password is transmitted in said incoming call.

A system for connecting a computer with an incoming call over a telephone circuit, said system comprising:

• a first modem connected to said telephone circuit for answering said incoming call without emitting an audible carrier tone;
• a second modem connected to said computer;
• controller means, connected to said first modem and said second modem, for controlling said second modem in response to a valid incoming call being received through said first modem so that said computer is communicated through both said second modem and said first modem to said telephone circuit to receive said valid incoming calls, said controller means comprising:
• a dual tone multiple frequency decoder for decoding analog signals, transmitted in said incoming call, into corresponding digital signals,
• entry code select means for selectably defining an entry code,
• entry code compare means, responsive to said signal decoder and said entry code select means, for determining whether said digital signals designate said entry code,
• a modem ring circuit, responsive to said entry code compare means determining that said digital signals designate said entry code, for generating an internal call and for transmitting said internal call to said second modem, so that upon answering said internal call, said second modem and said computer are in communication with said telephone circuit through said first modem,
• a modem hang-up circuit, responsive to said entry code compare means determining that said digital signals do not designate said entry code, for disconnecting said first modem from said incoming call, and
• means for generating and transmitting a voice response through said first modem upon said first modem receiving said incoming call and before said second modem and said computer are in communication with said telephone circuit through said first modem;
• and
• means, connected between said computer and said first and second modems, for disconnecting said modems from said incoming call when said first modem, said second modem, and said computer are all in communication with said telephone circuit and an incorrect password is transmitted in said incoming call.