Coded phone security system

Claim 1

A coded phone security system comprising: a ring integrator; means for creating an enabling timing pulse in response to an output from said ring integrator; means for placing an "off-hook" equivalent impedance on a telephone line during the duration of said timing pulse; a first optical isolator coupled to the telephone line via a normally open relay contact controlled by a relay coil responsive to said timing pulse; means for connecting said first optical isolator to a telephone line during the duration of said timing pulse; a second optical isolator for providing an enabling connection between said first optical isolator and said telephone line irrespective of the presence of said timing pulse; decoder means responsive to said telephone line through said first optical isolator; an annunciation means responsive to an output from said decoder indicative of the detection of a properly configured code; and reset means responsive to said telephone line via said second optical isolator for resetting said coded phone security system when said telephone line transitions from an "off-hook" condition to an "on-hook" condition.

Claim 21

A method for providing a coded security access system to a telephone handset, including the steps of: intercepting and integrating incoming ring pulses on the telephone line; generating an enabling pulse in response to a predetermined value of the integrated incoming ring pulses; generating a timing pulse in response to the enabling pulse; answering the incoming telephone call by placing an "off-hook" emulating impedance across the telephone line for the duration of the timing pulse; establishing an isolated interconnection between the telephone line and a decoder for the duration of the timing pulse by energizing a relay via said timing pulse to close a set of normally open relay contacts and thereby connect an optical isolator between said telephone line and said decoder; decoding incoming data on the telephone line for the duration of the timing pulse; establishing an alternate means for holding the telephone line in an "off-hook" condition irrespective of the presence or absence of the timing pulse; and simultaneously turning off the alternate means for holding the telephone line in an "off-hook" condition, breaking the isolated interconnection to the telephone line, removing the "off-hook" emulation and resetting the decoder circuits.

Claim 22

A method for providing a coded security access system to a telephone handset, including the steps of: intercepting and integrating incoming ring pulses on the telephone line; generating an enabling pulse in response to a predetermined value of the integrated incoming ring pulses; generating a timing pulse in response to the enabling pulse; answering the incoming telephone call by placing an "off-hook" emulating impedance across the telephone line for the duration of the timing pulse; establishing an isolated interconnection between the telephone line and a decoder for the duration of the timing pulse by energizing a relay via said timing pulse to close a set of normally open relay contacts and thereby connect an optical isolator between said telephone line and said decoder; decoding incoming data on the telephone line for the duration of the timing pulse; establishing an alternate means for holding the telephone line in an "off-hook" condition irrespective of the presence or absence of the timing pulse; and simultaneously turning off the alternate means for holding the telephone line in an "off-hook" condition, breaking the isolated interconnection to the telephone line, removing the "off-hook" emulation and resetting the decoder circuits.