Loop extender

Claim 2

A loop extender for use in a telephone system for increasing the signaling and supervisory range of a central office having a reversible office battery and a source of a.c. ringing voltage comprising, in combination, a tip side booster circuit inserted in the tip line and including a pair of oppositely pOlarized auxiliary voltage sources, a ring side booster circuit inserted in the ring line and including a pair of oppositely polarized auxiliary voltage sources, each of said booster circuits having an input terminal coupled to the office battery and an output terminal connected to the subscriber''s loop circuit, polarity sensitive means for detecting the polarity of the voltage at the input terminals and for concurrently and independently switching the appropriate one of each pair of the auxiliary sources into the respective tip and ring lines of the subscriber''s loop circuit so as to be in additive polarity to the office battery, and means responsive to the presence of a ringing voltage on the loop circuit for effectively disabling said polarity sensitive means to prevent said polarity sensitive means from following the a.c. reversals of the ringing voltage.

Claim 3

The combination as claimed in claim 1 wherein time delay means are coupled in circuit with the polarity sensitive means, said time delay means presenting, in the absence of ringing voltage, a time constant such that the polarity of the auxiliary sources changes promptly in step with rapid supervisory changes in the polarity of the office battery, and wherein said means responsive to the presence of ringing voltage serves to increase the time constant so that the polarity sensitive means is prevented from following the a.c. reversals of the ringing voltage.

Claim 4

The combination as claimed in claim 1 in which a current limiter is provided for limiting the current flow in the sources of auxiliary voltage.

Claim 5

The combination as claimed in claim 1 in which each source of auxiliary voltage has an a.c. input and a d.c. output, and in which a d.c. to a.c. inverter is provided supplying the a.c. inputs.

Claim 6

The combination as claimed in claim 4 in which means are provided for actuating the inverter only when current flows in the loop circuit.

Claim 7

A loop extender for use in a telephone system for increasing the signaling and supervisory range of a central office having a reversible office battery and source of a.c. ringing voltage comprising, in combination, a tip side booster circuit inserted in the tip line and including a pair of oppositely polarized sources of d.c. auxiliary voltage, a ring side booster circuit inserted in the ring line and including a pair of oppositely polarized sources of d.c. auxiliary voltage, each of said booster circuits having an input terminal coupled to the office battery and an output terminal connected to the subscriber''s loop circuit, each of the auxiliary sources being of the type using a transformer and rectifier intended for energization with a.c. voltage, a d.c. to a.c. inverter having its input connected to the office battery and having its output connected to the transformers, polarity sensitive means for detecting the polarity of the voltage at the input terminals and for switching the auxiliary sources into the respective tip and ring lines of the subscriber''s loop circuit so as to be in additive polarity to the office battery, and means responsive to flow of current in the loop for concurrently enabling the inverter so that the auxiliary sources of voltage are effective only when the subscriber''s loop circuit is in use.

Claim 8

A loop extender for use in a telephone system for increasing the signaling and supervisory range of a central office having a reversible office battery and source of a.c. ringing voltage comprising, in combination, a tip side booster circuit inserted in the tip line and including a pair of oppositely polarized sources of d.c. auxiliary voltage, a ring side booster circuit inserted in the ring line and including a pair of oppositely polarized sources of d.c. auxiliary voltage, each of said booster circuits having an input terminal coupled to the office battery and an output terminal connected to the subscriber''s loop circuit, each of the auxiliary sources being of the type using a transformer and rectifier intended for energization with a.c. voltage, a d.c. to a.c. inverter having its input connected to the office battery and having its output connected to the transformers, polarity sensitive means for detecting the polarity of the voltage at the input terminals and for switching the auxiliary sources into the respective tip and ring lines of the subscriber''s loop circuit so as to be in additive polarity to the office battery, and means responsive to flow of current in the loop for concurrently enabling the inverter so that the auxiliary sources of voltage are effective only when the subscriber''s loop circuit is in use.

Claim 9

The combination as claimed in claim 6 in which means are provided for limiting the current furnished by the inverter thereby to limit the loop current when the loop extender is employed in a short loop.

Claim 10

A loop extender for use in a telephone system for increasing the signaling and supervisory range of a central office having a reversible office battery and source of a.c. ringing voltage comprising, in combination, a tip side booster circuit inserted in the tip line and including a source of d.c. auxiliary voltage, a ring side booster circuit inserted in the ring line and including a source of d.c. auxiliary voltage, each of said booster circuits having an input terminal coupled to the office battery and an output terminal connected to tHe subscriber''s loop circuit, polarity sensitive means including a photosensitive series resistor for detecting the polarity of the voltage at the input terminals and for concurrently switching respective ones of said auxiliary sources into the subscriber''s circuit in additive polarity to the office battery, time delay means coupled in circuit with the polarity sensitive means for presenting, in the absence of ringing voltage, a time constant such that the polarity of the auxiliary sources changes promptly in step with rapid supervisory changes in the polarity of the office battery, and means concurrently responsive to the application of ringing voltage for increasing said time constant so as to effectively disable said polarity sensitive means to prevent said polarity sensitive means from following the a.c. reversals of ringing voltage, said ringing voltage responsive means being in the form of a gaseous discharge lamp connected in circuit between the tip and ring lines and having a high ionization level so as to illuminate the photosensitive resistor to change the resistance thereof only in the presence of ringing voltage.

Claim 11

A loop extender for use in a telephone system for increasing the signaling and supervisory range of a central office having a reversible office battery and source of a.c. ringing voltage comprising, in combination, a tip side booster circuit inserted in the tip line and including a source of d.c. auxiliary voltage, a ring side booster circuit inserted in the ring line and including a source of d.c. auxiliary voltage, each of said booster circuits having an input terminal coupled to the office battery and an output terminal connected to tHe subscriber''s loop circuit, polarity sensitive means including a photosensitive series resistor for detecting the polarity of the voltage at the input terminals and for concurrently switching respective ones of said auxiliary sources into the subscriber''s circuit in additive polarity to the office battery, time delay means coupled in circuit with the polarity sensitive means for presenting, in the absence of ringing voltage, a time constant such that the polarity of the auxiliary sources changes promptly in step with rapid supervisory changes in the polarity of the office battery, and means concurrently responsive to the application of ringing voltage for increasing said time constant so as to effectively disable said polarity sensitive means to prevent said polarity sensitive means from following the a.c. reversals of ringing voltage, said ringing voltage responsive means being in the form of a gaseous discharge lamp connected in circuit between the tip and ring lines and having a high ionization level so as to illuminate the photosensitive resistor to change the resistance thereof only in the presence of ringing voltage.

Claim 12

The combination as claimed in claim 8 in which the polarity sensitive means includes a feedback circuit and in which the photosensitive series resistor is in series with the feedback circuit so that when the lamp is lit the feedback circuit is fully effective to increase the time constant of the polarity sensitive means to the point where it is unresponsive to a.c. reversals of the ringing voltage.

Claim 13

A loop extender for use in a telephone system for increasing the signaling and supervisory range of a central office having a reversible office battery and source of a.c. ringing voltage which is substantially higher than the office battery voltage, said loop extender comprising, in combination, a tip side booster circuit inserted in the tip line and including a source of d.c. auxiliary voltage, a ring side booster circuit inserted in the ring line and including a source of d.c. auxiliary voltage, each of said booster circuits having an input terminal coupled to the office battery and an output terminal connected to the subscriber''s loop circuit, polarity sensitive means for detecting the polarity of the voltage at the input terminals and for concurrently switching respective ones of said auxiliary sources into the subscriber''s circuit in additive polarity to the office battery, and means concurrently responsive to the application of ringing voltage for effectively disabling said polarity sensitive means to prevent said polarity sensitive means from following the a.c. reversals of the ringing voltage, said ringing voltage responsive means being set to respond only to voltage on the order of the ringing voltage while being unresponsive to voltage on the order of battery voltage.

Claim 14

A loop extender for use in a telephone system for increasing the signaling and supervisory range of a central office having a reversible office battery and source of a.c. ringing voltage which is substantially higher than the office battery voltage, said loop extender comprising, in combination, a tip side booster circuit inserted in the tip line and including a source of d.c. auxiliary voltage, a ring side booster circuit inserted in the ring line and including a source of d.c. auxiliary voltage, each of said booster circuits having an input terminal coupled to the office battery and an output terminal connected to the subscriber''s loop circuit, polarity sensitive means for detecting the polarity of the voltage at the input terminals and for concurrently switching respective ones of said auxiliary sources into the subscriber''s circuit in additive polarity to the office battery, and means concurrently responsive to the application of ringing voltage for effectively disabling said polarity sensitive means to prevent said polarity sensitive means from following the a.c. reversals of the ringing voltage, said ringing voltage responsive means being set to respond only to voltage on the order of the ringing voltage while being unresponsive to voltage on the order of battery voltage.