Telephone line automatic prefix dialer

Apparatus for automatically dialing a predetermined code when a calling party institutes a call on a telephone network and for selectively canceling the effect of automatically dialing the predetermined code, the apparatus comprising:

• A) an off-hook detector having an input and an output, said input of said off-hook detector being connected to the telephone line of the calling party to detect an off-hook condition on the telephone line of the calling party and to provide an initiating signal at said off-hook detector output upon detection of an off-hook condition;
• B) a first time period determination circuit having an input connected to said output of said off-hook detector and responding to the presence of a first initiating signal by starting a first time period;
• C) an automatic dialer having an input and an output and storing a predetermined code, said automatic dialer input being connected to said first time period determination circuit and said automatic dialer output being connected to the telephone line of the calling party;
• 1) said automatic dialer being responsive to the starting of the first time period by dialing the stored predetermined code, thereby automatically applying the stored predetermined code to the telephone line of the calling party before the calling party dials the telephone number of a receiving party;
• D) a second time period determination circuit having an input coupled to said output of said off-hook detector and responding to the presence of an initiating signal occurring during the first time period by starting a second time period;
• E) said second time period determination circuit having an output coupled to the telephone line of the calling party such that, during the second time period, a hang-up condition is emulated on the telephone line of the calling party and, at the end of the second time period, when within the first time period, an off-hook condition is again detected by said off-hook detector, such that a second initiation signal is applied to said input of said first time period determination circuit;
• and
• F) said first time period determination circuit including means for inhibiting said second initiating signal from extending the first time period;
• whereby, if the calling party flashes the telephone line within the first time period and after the predetermined code has been dialed by the automatic dialer, a new dial tone is obtained and the caller can manually enter a telephone number which may include a prefix code different from the predetermined code.