Long line adapter circuit usable with increased power supply

Claim 2

A long line adapter circuit for connecting a telephone central office to a subscriber subset to compensate for any extraordinary combined length of a subscriber loop and a central office loop, said subscriber subset being of the type having a receiver that is maintainable in an on-hook condition or an offhook condition, said subscriber loop being adapted to be opened and closed by operation of the subset, said telephone central office equipped to transmit ringing signals, said adapter circuit comprising: a central office loop circuit adapted to be connected to a telephone central office by a central office loop and including switching means for being connected to said central office loop to effectively open and close said central office loop; a subscriber loop circuit adapted to be connected to a telephone subscriber subset by a subscriber loop and to a source of direct current power, said subscriber loop circuit including: pulsing means, connected in said subscriber loop, for providing a control signal when the subscriber loop is closed by operation of said subset, said control signal effecting operation of said switching means to close said central office loop; voltage increasing means, adapted to be operatively connected to any direct current power supply that is coupled to said subscriber loop circuit, for increasing by a predetermined amount the voltage applied to said subscriber loop circuit and said subscriber loop; sensing means for providing an off-hook signal in response to said receiver being in an off-hook condition, said off-hook signal being applied to said voltage increasing means to enable the operation thereof for the duration of any off-hook signal; safety means, connected to said pulsing means and said sensing means, for simultaneously preventing false operation of said pulsing means and said sensing means by the transmission of said ringing signals by shunting said pulsing means and said sensing means which are connected in series; and means for inductively coupling said central office loop circuit and said subscriber loop circuit.

Claim 3

The apparatus defined by claim 1 wherein said central office loop circuit includes ringing detector means for detecting ringing signals transmitted from said telephone central office and for enabling said ringing signals to be applied to said subscriber subset, said safety means being operatively controlled by said ringing detector means to operate in response to the detection of ringing signals by said ringing detecTor means.

Claim 4

The apparatus defined by claim 1 wherein said subscriber loop circuit includes a tip lead and a ring lead which are each adapted to be effectively connected to said subscriber subset by said subscriber loop and to a direct current power supply, said pulsing means including a first transistor coupled in said tip lead to be rendered conductive in response to said subscriber loop being closed by operation of said subset.

Claim 5

The apparatus defined by claim 3 wherein said safety means comprises a second transistor connected to shunt said first transistor, said first transistor being short circuited in response to said second transistor being rendered conductive.

Claim 6

The apparatus defined by claim 2 wherein said subscriber loop circuit includes a tip lead and a ring lead which are each adapted to be effectively connected to said subscriber subset by said subscriber loop and to a direct current power supply, said pulsing means including a first transistor coupled in said tip lead to be rendered conductive in response to said subscriber loop being closed by operation of said subset.

Claim 7

The apparatus defined by claim 5 wherein said safety means comprises a second transistor connected to shunt said first transistor, said first transistor being short circuited in response to said second transistor being rendered conductive.

Claim 8

The apparatus defined by claim 6, said sensing means comprising a third transistor serially connected with said first transistor such that said first and third transistors are both responsive to said subscriber loop being closed, said first and third transistors both being short circuited by said second transistor being rendered conductive.

Claim 9

A long line adapter circuit for being connected between a telephone central office and a telephone to compensate for undesired attenuation of signals by the extraordinary length of the telephone loop formed by the tip and ring telephone lines connecting the telephone to the central office, said telephone having a receiver adapted for an on-hook condition or an off-hook condition, said central office being adapted for sending ringing signals, said long line adapter circuit including: a pair of transformers interposed between said central office and said telephone by being connected in said tip and ring telephone lines, said transformers each having primary and secondary coils, the primary coils of said transformers connected in series between the tip and ring telephone lines connected to the central office to form a central office loop, the secondary coils connected in series between the tip and ring telephone lines connected to the telephone to form a subscriber loop, said central office loop being inductively coupled to said subscriber loop by said transformers; a central office loop circuit connected between said primary coils, said central office loop circuit including switching means for selectively opening or closing a resistive path between said primary coils; and a subscriber loop circuit connected to said secondary coils, said subscriber loop circuit including: pulsing means for providing a control signal when said receiver is in an off-hook condition, said control signal effecting operation of said switching means to close said resistive path between said primary coils; a pair of terminals for being connected to a source of direct current power; voltage booster means for increasing by a predetermined amount the voltage applied to said subscriber loop circuit by any source of direct control power connected to said pair of terminals; sensing means for providing an off-hook signal when said receiver is in an off-hook condition, said off-hook signal being applied to said voltage booster means to enable operation thereof for the duration of said off-hook signal, wherein said pulsing means, said sensing means, said pair of terminals and said inverter means are effectively connected in series between said secondary coils.

Claim 10

A long line adapter circuit for being connected between a telephone central office and a telephone to compensate for undesired attenuation of signals by the extraordinary length of the telephone loop formed by the tip and ring telephone lines connecting the telephone to the central office, said telephone having a receiver adapted for an on-hook condition or an off-hook condition, said central office being adapted for sending ringing signals, said long line adapter circuit including: a pair of transformers interposed between said central office and said telephone by being connected in said tip and ring telephone lines, said transformers each having primary and secondary coils, the primary coils of said transformers connected in series between the tip and ring telephone lines connected to the central office to form a central office loop, the secondary coils connected in series between the tip and ring telephone lines connected to the telephone to form a subscriber loop, said central office loop being inductively coupled to said subscriber loop by said transformers; a central office loop circuit connected between said primary coils, said central office loop circuit including switching means for selectively opening or closing a resistive path between said primary coils; and a subscriber loop circuit connected to said secondary coils, said subscriber loop circuit including: pulsing means for providing a control signal when said receiver is in an off-hook condition, said control signal effecting operation of said switching means to close said resistive path between said primary coils; a pair of terminals for being connected to a source of direct current power; voltage booster means for increasing by a predetermined amount the voltage applied to said subscriber loop circuit by any source of direct control power connected to said pair of terminals; sensing means for providing an off-hook signal when said receiver is in an off-hook condition, said off-hook signal being applied to said voltage booster means to enable operation thereof for the duration of said off-hook signal, wherein said pulsing means, said sensing means, said pair of terminals and said inverter means are effectively connected in series between said secondary coils.

Claim 11

The long line adapter circuit defined by claim 8 further including: contact means for selectively completing direct electrical connections of the tip and ring telephone lines between said central office and said telephone, said direct electrical connections effectively by-passing said transformers; and ringing detector means for detecting ringing signals transmitted from said central office to signal said telephone, said ringing detector means connected in parallel to said switching means, said ringing detector means being shunted when said switching means is operated to close said resistive path between said primary coils.

Claim 12

The long line adapter circuit defined by claim 9 further including: safety means, responsive to operation of said ringing detector means by the reception of ringing signals, for preventing false operation of said pulsing means and said sensing means.