Telephone line loop current regulator
First Claim
1. A telephone line d.c. loop current regulator comprising:
- a gyrator circuit connected across the line, a field effect transistor connected in series with a resistor across the line, the field effect transistor forming the amplifying means of the gyrator circuit, means responsive to current flow through the field effect transistor for regulating the d.c. current through the field effect transistor, and loop current detection means connected across the resistor.
1 Assignment
0 Petitions
Accused Products
Abstract
A telephone line loop current regulator combines the functions of current regulation, current detection, loop disconnect signalling and speech switching. It comprises a gyrator circuit formed by resistor (R1), capacitor (C1), transistor (T1) and resistor (R3). Loop current is regulated by transistor (T1) and resistor (R3) while loop current detection is achieved by monitoring the voltage across resistor (R3) by an opto-diode which forms part of an opto-electronic coupler (OP2). Speech switching is performed by transistor (T3) which also monitors the voltage across resistor (R3) so that speech is switched onto the line via transformer (TR1) when d.c. loop current is present. Line seizure and loop disconnect signalling are carried out by switching the opto-coupler (OP1) to turn the transistor (T1) on and off.
-
Citations
28 Claims
-
1. A telephone line d.c. loop current regulator comprising:
- a gyrator circuit connected across the line, a field effect transistor connected in series with a resistor across the line, the field effect transistor forming the amplifying means of the gyrator circuit, means responsive to current flow through the field effect transistor for regulating the d.c. current through the field effect transistor, and loop current detection means connected across the resistor.
- View Dependent Claims (2, 3)
-
4. A telephone line d.c. loop current regulator comprising:
- a gyrator circuit connected across the line, a field effect transistor connected in series with a resistor across the line, the field effect transistor forming the amplifying means of the gyrator circuit, means for regulating the d.c. current through the field effect transistor, loop current detection means connected across the resistor, and an electronic switch in the gate circuit of the field effect transistor which is effective when closed to turn on the field effect transistor to cause the line to be seized.
- View Dependent Claims (5, 6, 7, 8, 9, 10, 11, 12)
-
13. A telephone line d.c. loop current regulator comprising:
- a gyrator circuit connected across the line, a field effect transistor connected in series with a resistor across the line, the field effect transistor forming the amplifying means of the gyrator circuit, means for regulating the d.c. current through the field effect transistor, loop current detection means connected across the resistor, and a voltage reference diode connected between the gate of the field effect transistor and a loop conductor to which the resistor is connected.
- View Dependent Claims (14, 15)
-
16. A telephone line loop current regulator comprising:
-
a gyrator circuit which includes a field effect transistor connected in a first series circuit with a first resistor across first and second wires of the telephone line and further comprising a capacitor and a second resistor connected in a second series circuit across said first and second wires of the telephone line, means coupled to the field effect transistor for regulating DC current through the field effect transistor, and loop current detection means coupled across the first resistor. - View Dependent Claims (17, 18, 19, 20, 21, 22, 23, 24)
-
-
25. A telephone line d.c. loop current regulator comprising:
- a gyrator circuit connected across the line, a field effect transistor connected in series with a resistor across the line, the field effect transistor forming the amplifying means of the gyrator circuit, means for regulating the d.c. current through the field effect transistor, loop current detection means connected across the resistor, a resistive potential divider connected across the telephone line, said potential divider including a further transistor which is controlled so as to be turned off when the field effect transistor is turned off, a capacitor connected between the gate of the field effect transistor and a loop conductor which is connected to the resistor, and means for coupling a point on the potential divider to the gate of the field effect transistor.
- View Dependent Claims (26, 27, 28)
Specification