US 4,396,809 AGranted

Maintenance termination unit

AssigneeBell Telephone Laboratories, Incorporated

InventorJames E. Brunssen

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Abstract

A maintenance termination unit (10) comprises a voltage sensitive switch (30,50) connected permanently in series with each loop conductor (11,13) and an impedance termination unit (18) connected permanently across the loop conductors. Each voltage sensitive switch (30 or 50) comprises a triac (32) connected in series with a loop conductor (11 or 13), a capacitor (34) and resistor (36) connected across the terminals of the triac, and a bilateral switch (60) connected between one of the terminals and the gate electrode of the triac. In response to a signal having a voltage greater than the threshold voltage of the switch, the capacitor is charged to the threshold voltage, thereupon the capacitor discharges insuring that the triac is gated to the ON state.

Claims6

Dependent claims

A maintenance termination unit (10) connected in series with a telephone subscriber loop comprising tip conductor (11) and ring conductor (13) for determining whether a fault in said subscriber loop is located on the telephone set (12) side or the central office side of said maintenance termination unit, said maintenance termination unit comprising

an impedance termination network connected across said tip and ring conductors,
a first voltage sensitive switch (30) responsive to the magnitude of signals on and connected in series with said tip conductor,
a second voltage sensitive switch (50) responsive to the magnitude of signals on and connected in series with said ring conductor,
said first and second voltage sensitive switches being substantially identical, each of said voltage sensitive switches comprising
a triac (32) comprising first and second terminals and a gate lead (47) said terminals being connected in series with said tip or ring conductor,
a bilateral switch (60) connected between one of said terminals and said gate lead of said triac, and
a capacitor (34) and a resistor (36) connected across said first and second terminals of said triac.

4 more elements

Dependencies are inferred from the claim text.