Battery feed circuit for subscriber line

Claim 2

A battery feed circuit for a subscriber line operative to feed constant currents to a pair of a first subscriber line (A) and a second subscriber line (B) via a first feed circuit part (B a ) and a second feed circuit part (B b ), respectively, characterised in that first and second reference voltage output circuits (RV 1 ,RV 0 ) and an intermediate voltage output circuit (IV) are further employed therein, the first and second reference voltage output circuits (RV 1 ,RV 0 ) being operative to produce first and second reference voltages obtained by dividing voltage between a ground level (GD) and a power source level (-V BB ) and to apply the thus output reference voltages to said first (B a ) and second (B b ) feed circuit parts, respectively, for activation of the same, and the intermediate voltage output circuit (IV) being operative to produce an intermediate voltage between the first and second subscriber lines (A,B) and to superpose the same onto each of said first and second reference voltages.simultaneously.

Claim 3

A battery feed circuit as set forth in claim 1, wherein said first reference voltage output circuit (RV 1 ) is set up with first and second resistors (R a1 ,R b1 ) connected in series and said second reference voltage output circuit (RV O ) is set up with third and fourth resistors (R b0 ,R a0 ) connected in series, and the first through fourth resistors being connected in series between the ground (GD) and the power source (-V BB ).

Claim 4

A battery feed circuit as set forth in claim 2, wherein said intermediate voltage output circuit (IV) is comprised of a fifth resistor (R c0 ) and a sixth resistor (R c1 ), connected in series between said first and second subscriber lines (A,B), and an amplifier (A2), the input of the amplifier (A 2 ) being connected with an intermediate connecting point (M 1 ) of the fifth (R c0 ) and sixth (R cl ) resistors and the output thereof being connected with an intermediate connecting point (M 2 ) of the second (R b1 ) and third (R b0 ) resistors.

Claim 5

A battery feed circuit as set forth in claim 3, wherein said first feeder part (B a ) includes at least a first operational amplifier (A 1 ) receiving said first reference voltage at one of its input terminals, a first transistor (T rl ) connecting, at its base, the output terminal of the first operational amplifier (A 1 ), and a seventh resistor (R el ) connected, between said power source and said first subscriber line (A), in series with the first transistor (Trl), and said second feed circuit part (B b ) includes at least a second operational amplifier (A 0 ) receiving said second reference voltage at one of its input terminals, a second transistor (T rO ) connecting, at its base, the output terminal of the second operational amplifier (A 0 ), and an eighth resistor (R e0 ) connected, between said ground (G D ) and said second subscriber line (B), in series with the second transistor (T r0 ).

Claim 6

A battery feed circuit as set forth in claim 4, wherein the other input terminal of said first operational amplifier (A 1 ) is directly connected to an intermediate connecting point between said seventh resistor (R e1 ) and said first transistor (T rl ) and the other input terminal of said second operational amplifier (A 0 ) is directly connected to an intermediate connecting point between said eighth resistor (R e0 ) and said second transistor (T r0 ).

Claim 7

A battery feed circuit as set forth in claim 4, wherein said other input terminal of said first operational amplifier (A 1 ) is connected, via a ninth resistor (R f1 ), to said intermediate connecting point close to said first transistor (T rl ), the ninth resistor (R fl ) being further connected with a series-connected tenth resistor (R s1 ) and a first capacitor (C 1 ) and which is led to said ground, said other input terminal of said second operational amplifier (A 0 ) is connected, via an eleventh resistor (R f0 ), to said intermediate connecting point close to said second transistor (T r0 ), the eleventh resistor (R f0 ) being further connected with a series-connected twelfth resistor (R s0 ) and a second capacitor (C 0 ) which is led to said power source.

Claim 8

A battery feed circuit as set forth in claim 6, wherein a thirteenth resistor (R dl ) is provided between said first transistor (T r1 ) and said first operational amplifier (A 1 ) and a fourteenth resistor ( RdO ) is provided between said second transistor (T r0 ) and said second operational amplifier (A 0 ).

Claim 9

A battery feed circuit as set forth in claim 7, wherein first and second zener diodes (ZD 1 ,ZD 0 ) connected in series between said ground and said power source, and a fifteenth resistor (R g ) are further provided and the fifteenth resistor (Rg) is connected, at its one end, with an intermediate connecting point (M 2 ) between the first and second zener diodes, the other end of which fifteenth resistor (Rg) is connected to the output of said amplifier (A 2 ), while the one end of the fifteenth resistor is also connected to the intermediate connecting point between said second and third resistors C b1 ,R b0 ).

Claim 10

A battery feed circuit as set forth in claim 3, wherein said amplifier (A 2 ) is a voltage follower.

Claim 11

A battery feed circuit as set forth in claim 9, wherein said voltage follower has a gain of 1.

Claim 12

A battery feed circuit as set forth in any one of claims 6 to 8 , wherein said tenth ( Rsl ) and twelfth (R s0 ) resistors and said first and second capacitors (C 1 ,C 0 ) are all fabricated, as a whole, by a series-connected sixteenth resistor and a third capacitor connected between said other input terminals of said first and second operational amplifiers (A 1 ,A 0 ).

Claim 13

A battery feed circuit for a subscriber line operative to feed constant currents to a pair of a first subscriber line (A) and a second subscriber line (B) via a first feed circuit part (B ) and a second feed circuit part (B b ), respectively, characterised in that the first feed circuit part (B a ) is comprised of a first operational amplifier (A 1 ) and a first transistor (T r1 ), the second feed circuit part (B b ) being comprised of a second operational amplifier (A 0 ) and a second transistor (T r0 ), the first and second feed circuit parts being provided with first through eighth resistors and a DC-cut capacitor, said first through third resistors (R 1 ,R 2 ,R 3 ) being connected in series between a ground (GD) and a power source (-V BB ), an intermediate connecting point (P a ) between the first and second resistors (R 1 ,R 2 ) and an intermediate connecting point (P b ) between the second and third resistors (R 2 ,R 3 ) being connected with respective first input terminals of said second (A 0 ) and first (A 1 ) operational amplifiers, said fourth and fifth resistors (R 4 ,R 5 ) being connected, each at one of their ends, to the ground (GD) and the power source (-V BB ), respectively, and connected, each at the other of their ends, to said second and first transistors (Tr 0 ,Tr1), respectively, said sixth resistor (R 6 ) being connected between a second input terminal of said second operational amplifier (A 0 ) and said second transistor (T r0 ), said seventh resistor (R 7 ) being connected between a second input terminal of said first operational amplifier ( AI ) and said first transistor (T rl ), said eighth resistor (R 8 ) and said DC-cut capacitor (C 01 ), connected in series, being connected between said second input terminals of respective said first and second operational amplifiers.

Claim 14

A battery feed circuit for a subscriber line operative to feed constant currents to a pair of a first subscriber line (A) and a second subscriber line (B) via a first feed circuit part (B ) and a second feed circuit part (B b ), respectively, characterised in that the first feed circuit part (B a ) is comprised of a first operational amplifier (A 1 ) and a first transistor (T r1 ), the second feed circuit part (B b ) being comprised of a second operational amplifier (A 0 ) and a second transistor (T r0 ), the first and second feed circuit parts being provided with first through eighth resistors and a DC-cut capacitor, said first through third resistors (R 1 ,R 2 ,R 3 ) being connected in series between a ground (GD) and a power source (-V BB ), an intermediate connecting point (P a ) between the first and second resistors (R 1 ,R 2 ) and an intermediate connecting point (P b ) between the second and third resistors (R 2 ,R 3 ) being connected with respective first input terminals of said second (A 0 ) and first (A 1 ) operational amplifiers, said fourth and fifth resistors (R 4 ,R 5 ) being connected, each at one of their ends, to the ground (GD) and the power source (-V BB ), respectively, and connected, each at the other of their ends, to said second and first transistors (Tr 0 ,Tr1), respectively, said sixth resistor (R 6 ) being connected between a second input terminal of said second operational amplifier (A 0 ) and said second transistor (T r0 ), said seventh resistor (R 7 ) being connected between a second input terminal of said first operational amplifier ( AI ) and said first transistor (T rl ), said eighth resistor (R 8 ) and said DC-cut capacitor (C 01 ), connected in series, being connected between said second input terminals of respective said first and second operational amplifiers.