CA1111586A - Circuit for electronic subscriber feed - Google Patents
Circuit for electronic subscriber feedInfo
- Publication number
- CA1111586A CA1111586A CA292,254A CA292254A CA1111586A CA 1111586 A CA1111586 A CA 1111586A CA 292254 A CA292254 A CA 292254A CA 1111586 A CA1111586 A CA 1111586A
- Authority
- CA
- Canada
- Prior art keywords
- input
- differential amplifier
- loop
- branch
- circuit arrangement
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04M—TELEPHONIC COMMUNICATION
- H04M19/00—Current supply arrangements for telephone systems
- H04M19/001—Current supply source at the exchanger providing current to substations
- H04M19/005—Feeding arrangements without the use of line transformers
Landscapes
- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Signal Processing (AREA)
- Interface Circuits In Exchanges (AREA)
- Devices For Supply Of Signal Current (AREA)
Abstract
Abstract of the Disclosure:
A circuit arrangement for an electronic subscriber feed has loop current supervision, ringing connection and hybrid for a transition from two to four-wire operation with mutually symmetrically connected current generators for communication facilities such as branch telephone exchanges. The current generators are operational amplifiers having transistors associated therewith, the operational amplifiers being opera-tive as pure voltage followers and having inverted inputs through which modulation of the loop current is controllable in a manner that dynamic self-balancing of said current genera-tors is increased by amplification of the modulation voltage.
A differential amplifier is associated with the operational amplifier and having an output and an input. A transistor is connected to the input of the differential amplifier and means are also provided for applying, with the loop open, a loop signal through the transistor connected to the input of the differential amplifier for controlling the differential amplifier so as to obtain a large hybrid attenuation in a manner that no a-c voltage reaches the output of the differential ampli-fier. The hybrid includes a complex line balancing network in combination with an impedance selected from a group consisting of a real-input resistance and a complex input impedance
A circuit arrangement for an electronic subscriber feed has loop current supervision, ringing connection and hybrid for a transition from two to four-wire operation with mutually symmetrically connected current generators for communication facilities such as branch telephone exchanges. The current generators are operational amplifiers having transistors associated therewith, the operational amplifiers being opera-tive as pure voltage followers and having inverted inputs through which modulation of the loop current is controllable in a manner that dynamic self-balancing of said current genera-tors is increased by amplification of the modulation voltage.
A differential amplifier is associated with the operational amplifier and having an output and an input. A transistor is connected to the input of the differential amplifier and means are also provided for applying, with the loop open, a loop signal through the transistor connected to the input of the differential amplifier for controlling the differential amplifier so as to obtain a large hybrid attenuation in a manner that no a-c voltage reaches the output of the differential ampli-fier. The hybrid includes a complex line balancing network in combination with an impedance selected from a group consisting of a real-input resistance and a complex input impedance
Description
Specification:
The invention relates to a circuit arrangement for an electronic subscriber feed with loop current supervision, ringing connection and hybrids for a transition from two- to four-wire operation with mutually symmetrically connected current generators for communication facilities, such as private branch telephone exchanges, especially.
Heretofore known feeding arrangements for telephone subscriber stations with central battery or current source are formed of feed coils, transformer and relay arrangements which, in telephone systems with one feeder, respectively, to each subscriber station, require a great expenditure of both space and money and, because of the close disposition of coils and transformers, foster or promote crosstalk. To reduce the mechanical outlay or expenditure, it has become known, for example, from the German Published Prosecuted Application DT-AS 1 199 827 which was published on September 2, 1965 in the name of Telefunken Patentverwertungsgesellschaft mbH, to use current generators.
Other feeding arrangements employ solid-state components, which eliminate choke coils and transformers and largely preclude crosstalk (German Published Non-Prosecuted Application DT-OS 20 20 527 which was publlshed on December 23, 1970 in the name of International Standard Electric Corp.).
Such feeding arrangements may be combined with ringing current feed-in and a hybrid, and through loop current supervision, the initiation of the further switching of a connection by operation of a grounding key of a subscriber station may be evaluated, besides triggering the establishment of the connection, current stabilization during the operation of the ground-ing key being ensured. This arrangement for subscriber feeds is useful, preferably for house exchange equipment, as it does not fully meet the hybrid attenuation requirements for long loops.
~3 ~
llllS86 It is accordingly an object of the invention to provide a circuit arrangement for an electronic subscriber feed with a hybrid, which permits the use of long loops and is affected relatively little by tolerances of components.
With the foregoing and other objects in view, there is provided, in accordance with the invention, a circuit arrangement for an electronic subscriber feed with loop current supervision, ringing connection and hybrid for a transition from two to four-wire operation with mutually symmetrically connected current generators for communication facilities such as branch telephone exchanges, the current generators comprising, in a two-wire branch of the hybrid, operational amplifiers having respective transistors operatively connected therewith, said operational amplifiers being operative as pure voltage followers and having inverted inputs through which modulation of the loop current is controllable, dynamic self-balancing of said current generators being increased by amplification of a modulation voltage applied to said two-wire branch in an incoming line branch of a four-wire branch of the hybrid, a differential amplifier operatively connect-ed with said operational amplifiers and having an output connected to an outgoing line of said four-wire branch and an input, a transistor having a collector connected to said input of said differential amplifier, and means for applying, with the loop open, a loop signal through said transistor connected to said input of said differential amplifier for controlling said differential amplifier so as to obtain a large hybrid attenuation in a manner that no a-c voltage reaches said output of said differential amplifier, said hybrid comprising a complex line balancing network connected in said four-wire branch and an input impedance connected in said two-wire branch, said input impedance being selected from a group consisting of a real resistance and a complex impedance.
In accordance with another feature of the invention, the input of the differential amplifier is inverted and an amplifier is pro-1~11586 vi~ed for applying a countervoltage to the inverted input of thedifferential amplifier, with the loop closed, so as to obtain a large attenuation.
In accordance with a further ~eature of the invention, the circuit arrangement includes voice wires connected to the opera-tional amplifiers and having an external termination, the comple~ ¦
line balanclng netwokr having a frequency response correspondin~
to the ~requency response of the external termination o~ the v~ice wlres.
In accordance with an added feature of the invention, an R-C
component connected in shunt with the complex line balancing net-work is also included.
In accordance with an ad~itional feature of the invention, the circuit arrangement includes voice wires connected to the opera- ¦
tional amplifiers and having a load connected thereto, the complex input impedance a~d the complex line balancing network for the complex internal generator impedance having a frequency response corresponding to the load connected to the voice wiresO
In accordance with yet another feature of the invention, the circuit arrangement includes an incoming line branch connected to the operational amplifiers, and means cooperating with the operational amplifiers for converting an unbalanced input voltage applied to the incoming line branch to a balanced voltage at the voice wires.
In accordance with yet another ~eature of the invention, the circuit arrangement includes means for evaluating the loop compris- ¦
ing resistancesconnected to outputs of the operational amplifiers~
In accordance with a concomitant feature Or the invention, the circuit arrangement inclu~es voice wires connected to the opera-tional ampliriers, and balancing resistors respectively associated with the operational amplifiers and directly connected to the voice wires.
Other features which are considere~ as characteristic for the inventior arL~ set forth in the app~nded claim.~.
.1lthou~h the invention is illustrate~ an~ described herein a~
embodled ~n circuit for an electron~c subscriber fee~, it is nevertheless not intende~ to be llmited to th~ details shown, since various mod1fications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, how-ever, together with additlonal ob~ects and advantages thereof wlll be best understood from the following description when read in connection with the single figure of the drawlng which is a diagram of a circuit arrangement for two alternate embodiments of the invention and which shows only the features essential to the lnventionc Referring now to the drawing, it is noted that the supply system or feed is formed of two current generators which are disposed symmetrlcally to each other and for which operational amplifiers Jl and ~2 each in con~unction with a transistor~ are used. The advantage of the operational amplifiers Jl and J2 instead of transistors, for example, in a Darlington arrangement, is in the independence of the loop current of transistor parameters such as the base-emitter voltage, for example, which can fluctuate sharply.
The loop current is consequently determined exclusively by the voltages at the resistors Rl, R2, which are transm~tted to the terminals on the emitter side of the loop resistors R3 and R4, respectively, via the operational ampli~iers Jl, J20 In this regard, the operational amplifiers Jl, J2 operate as pure voltage followers, so that the potentials at the positive inputs of the ~r llllS86 amplifiers Jl, J2 an~ the potentials at the loop resistance R3, R4 are equal. The symmetrJ of the arrangement is ensured by the balancing resistors R5, R6, which are directly connecte~ to the voice wires A, B without the intermediary of any diodes. Through the direct connection, the tolerances of the protective resistors R7, R8, which serve to protect the feed against voltages on the wires of the subscriber loop or connected lines, are also equal-ized.
Modulation of the closed-circuit loop current occurs via the inverted inputs of the amplifiers Jl, J2. The associated re-sistances of R9, Rll and R10, R12 determine the rat;io of the modulation voltage to the moaulation current. If the resistances of R9 to R12 are equal, the modulation voltage at the capacitors C2, C3 is transmitted to the loop resistors R3, R4 with the gain 1. With increasing gain of the modulation arrangement by appropriate dimensioning, the a-c voltage gain of the positive inputs of the amplifiers Jl, J2 and, thereby, the ~ynamic self-or automatic balance are also improved.
For evaluating the loop, the inverter resistors R13, R14 are connected to the outputs of the amplifiers Jl, J2. Without these inverter resistors R13, R14, the same voltage wou1d be present at the loop resistors R3, R4, when the subscriber loop is open as well as closed, which could prevent evaluation of the loop. With in-creasing ratio of the resistance values o~ the inverter resistors R13~ R14 to those of ~he loop resistors R3, R4, the evaluation threshold for the loop signals also increases.
The amplifier J6 has a ga~n 1 and serves for inverting the signals coming from the preceding amplifier J4 and J~, respect-ively, for modulating the voice wire B.
-- llllS86 In order to achleve a large hybrtd attenuation if the subscriber loop is open, the differential amplifier J3 is driven into limit-ing via the transistor T by the loop signal at the point S, so that no a-c voltage can reach the point G of the outgoing branch of the hybridO
As a~orementioned, two circuit variants or embodiments of the hybrld arrangement are shown in the figure, both of which are described hereinafter in greater detail.
The first circuit variant has a real lnput resistance and there-~ore a real internal generator resistance and a complex line balanclng network whereby me;.sured transn~ssion values are obtained which correspond to conventional inductive hybrids.
The second circuit varlant is equipped with a complex input im-ped~nce and, consequently, with a complex internal generator im-pedance and with a complex line balancing network. The dimenslon-ing of the balancing networks depends upon the type of cable of the subscriber loop and.upon the internal impedence of the sub-scriber station.
In the embodiment of the circuit which has a real input resistance R15, the latter is connected between the polnts 1-1. The connection o~ the points 2-3 is severed and connectlon of the points 2-4 is maintained; tn the practical design of the circuit, the ampli~ier J5 and the llne balancing network N2 as well as the unidentifted resistor and capacitor associated there~th, are omitted~ The voltage present at the real input resistor R15 is transmitted via the differential amplifier J3 to the outgoing branch of the hybrid arrangement, point G.
The voltage present in the incoming direction at the point K is transmltted v~a the modulation circuit to the voice wires A, B
s~
1~11S86 and therefore, ~lso to thq inpuls of the differential amplifierJ30 In order to obtain ~ larg~e hybrid attenuation, a counter-voltage is applied to t.he inv~ ted input of the di~ferential amplifier J3 by the amplifier J51, so that there ls no voltage at the point G.
Under operating conditions iOe. lf the voltage present at the point K produces a ~requency-dependent voltage on the voice wires A, B, the ~requency response o~ the line balancing network N
must correspond to that of the external termination o~ the voice wires A, Bo Since the input resistance R15 together with the capacitor Cl is also frequency-dependent to a certain extent, the line balancing network N is shunted by an R-C member, the elec-trical data or values Or which correspond to those of the input resistance R15 and the capacitor Cl~
In the embodiment of the circuit which has a complex input im-pedance, a complex ~nput impedance Nl is connected between the polnts l-lo Connection of the points 2-3 is maintained and that of the points 2-4 is severed; the amplifier J51, the complex balancing network N with the R-C component thereof and the other-wise unidentified resistor associated therewith being omitted in the practical construction of the circuit. The circuit arrange-ment is formed in such a manner that the voltage at the voice wires A, B is transmitted as an unbalanced or asymmetric voltage to the point G o~ the outgo~ng branch of the hybrid via the dif~erential amplifier J3. An unbalanced or asymmetric voltage at the point K of the incoming branch is transmitte~ to the YoiCe wires A, B as a balanced or symmetric voltageO The frequency response of the complex input ir..pedance Nl, as well as the llne balancing network N2 for the co~plex internal generator impe~ance corresponds to the load on the voice wires A, Bo . -8-llllS86 The current flowing in the line balancing network N2 is converted by tne amplifier J5 into a control voltage for the current generators. The current delivered by the current generators to the parallel circuit consisting of the complex input impedance Nl and the subscriber stat~on consequently has the same frequency response as the current in the line balanc~ng network N2. Through appropriate selection of the gain of the operational amplifiers Jl, on the one hand, and J2 and J5, on the other hand, the voltage of the voice wires A, B is exactly equal to the voltage at the point K. The equality of these voltages ls utilized for the hybrid function of the arrangement. Wlth equal hybrld re-sistances R16 to ~21, the voltage at the point K is fed vla the amplifier J4 to the resistor R17 and counteracts with twice the amplitude the voltage from the voice wire A, which is thereby cancelled. Together with the voltage of the voice wire B, a common-mode signal is delivered therewith to the inputs of the differential amplifier J3 but is not taken into consideration.
The advantage of the last-described circuit variant is that the input impedance is matched to the impedance of the connected line. A telephone system constructed in this manner is very well matched to a line network. If, in additlon, the input impedance and the lnternal impedance of the subscriber station are matched to the line impedance, then good hybrid attenuation and side-tone reduction, respectively, can be obtained also with very short loops or connected linesO
The use of operat~onal amplifiers affords the realization o~
the balancing network N2 with physical or spatially small components, which have an impedance that is many times higher than that of conventional balancing networks.
_9_
The invention relates to a circuit arrangement for an electronic subscriber feed with loop current supervision, ringing connection and hybrids for a transition from two- to four-wire operation with mutually symmetrically connected current generators for communication facilities, such as private branch telephone exchanges, especially.
Heretofore known feeding arrangements for telephone subscriber stations with central battery or current source are formed of feed coils, transformer and relay arrangements which, in telephone systems with one feeder, respectively, to each subscriber station, require a great expenditure of both space and money and, because of the close disposition of coils and transformers, foster or promote crosstalk. To reduce the mechanical outlay or expenditure, it has become known, for example, from the German Published Prosecuted Application DT-AS 1 199 827 which was published on September 2, 1965 in the name of Telefunken Patentverwertungsgesellschaft mbH, to use current generators.
Other feeding arrangements employ solid-state components, which eliminate choke coils and transformers and largely preclude crosstalk (German Published Non-Prosecuted Application DT-OS 20 20 527 which was publlshed on December 23, 1970 in the name of International Standard Electric Corp.).
Such feeding arrangements may be combined with ringing current feed-in and a hybrid, and through loop current supervision, the initiation of the further switching of a connection by operation of a grounding key of a subscriber station may be evaluated, besides triggering the establishment of the connection, current stabilization during the operation of the ground-ing key being ensured. This arrangement for subscriber feeds is useful, preferably for house exchange equipment, as it does not fully meet the hybrid attenuation requirements for long loops.
~3 ~
llllS86 It is accordingly an object of the invention to provide a circuit arrangement for an electronic subscriber feed with a hybrid, which permits the use of long loops and is affected relatively little by tolerances of components.
With the foregoing and other objects in view, there is provided, in accordance with the invention, a circuit arrangement for an electronic subscriber feed with loop current supervision, ringing connection and hybrid for a transition from two to four-wire operation with mutually symmetrically connected current generators for communication facilities such as branch telephone exchanges, the current generators comprising, in a two-wire branch of the hybrid, operational amplifiers having respective transistors operatively connected therewith, said operational amplifiers being operative as pure voltage followers and having inverted inputs through which modulation of the loop current is controllable, dynamic self-balancing of said current generators being increased by amplification of a modulation voltage applied to said two-wire branch in an incoming line branch of a four-wire branch of the hybrid, a differential amplifier operatively connect-ed with said operational amplifiers and having an output connected to an outgoing line of said four-wire branch and an input, a transistor having a collector connected to said input of said differential amplifier, and means for applying, with the loop open, a loop signal through said transistor connected to said input of said differential amplifier for controlling said differential amplifier so as to obtain a large hybrid attenuation in a manner that no a-c voltage reaches said output of said differential amplifier, said hybrid comprising a complex line balancing network connected in said four-wire branch and an input impedance connected in said two-wire branch, said input impedance being selected from a group consisting of a real resistance and a complex impedance.
In accordance with another feature of the invention, the input of the differential amplifier is inverted and an amplifier is pro-1~11586 vi~ed for applying a countervoltage to the inverted input of thedifferential amplifier, with the loop closed, so as to obtain a large attenuation.
In accordance with a further ~eature of the invention, the circuit arrangement includes voice wires connected to the opera-tional amplifiers and having an external termination, the comple~ ¦
line balanclng netwokr having a frequency response correspondin~
to the ~requency response of the external termination o~ the v~ice wlres.
In accordance with an added feature of the invention, an R-C
component connected in shunt with the complex line balancing net-work is also included.
In accordance with an ad~itional feature of the invention, the circuit arrangement includes voice wires connected to the opera- ¦
tional amplifiers and having a load connected thereto, the complex input impedance a~d the complex line balancing network for the complex internal generator impedance having a frequency response corresponding to the load connected to the voice wiresO
In accordance with yet another feature of the invention, the circuit arrangement includes an incoming line branch connected to the operational amplifiers, and means cooperating with the operational amplifiers for converting an unbalanced input voltage applied to the incoming line branch to a balanced voltage at the voice wires.
In accordance with yet another ~eature of the invention, the circuit arrangement includes means for evaluating the loop compris- ¦
ing resistancesconnected to outputs of the operational amplifiers~
In accordance with a concomitant feature Or the invention, the circuit arrangement inclu~es voice wires connected to the opera-tional ampliriers, and balancing resistors respectively associated with the operational amplifiers and directly connected to the voice wires.
Other features which are considere~ as characteristic for the inventior arL~ set forth in the app~nded claim.~.
.1lthou~h the invention is illustrate~ an~ described herein a~
embodled ~n circuit for an electron~c subscriber fee~, it is nevertheless not intende~ to be llmited to th~ details shown, since various mod1fications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, how-ever, together with additlonal ob~ects and advantages thereof wlll be best understood from the following description when read in connection with the single figure of the drawlng which is a diagram of a circuit arrangement for two alternate embodiments of the invention and which shows only the features essential to the lnventionc Referring now to the drawing, it is noted that the supply system or feed is formed of two current generators which are disposed symmetrlcally to each other and for which operational amplifiers Jl and ~2 each in con~unction with a transistor~ are used. The advantage of the operational amplifiers Jl and J2 instead of transistors, for example, in a Darlington arrangement, is in the independence of the loop current of transistor parameters such as the base-emitter voltage, for example, which can fluctuate sharply.
The loop current is consequently determined exclusively by the voltages at the resistors Rl, R2, which are transm~tted to the terminals on the emitter side of the loop resistors R3 and R4, respectively, via the operational ampli~iers Jl, J20 In this regard, the operational amplifiers Jl, J2 operate as pure voltage followers, so that the potentials at the positive inputs of the ~r llllS86 amplifiers Jl, J2 an~ the potentials at the loop resistance R3, R4 are equal. The symmetrJ of the arrangement is ensured by the balancing resistors R5, R6, which are directly connecte~ to the voice wires A, B without the intermediary of any diodes. Through the direct connection, the tolerances of the protective resistors R7, R8, which serve to protect the feed against voltages on the wires of the subscriber loop or connected lines, are also equal-ized.
Modulation of the closed-circuit loop current occurs via the inverted inputs of the amplifiers Jl, J2. The associated re-sistances of R9, Rll and R10, R12 determine the rat;io of the modulation voltage to the moaulation current. If the resistances of R9 to R12 are equal, the modulation voltage at the capacitors C2, C3 is transmitted to the loop resistors R3, R4 with the gain 1. With increasing gain of the modulation arrangement by appropriate dimensioning, the a-c voltage gain of the positive inputs of the amplifiers Jl, J2 and, thereby, the ~ynamic self-or automatic balance are also improved.
For evaluating the loop, the inverter resistors R13, R14 are connected to the outputs of the amplifiers Jl, J2. Without these inverter resistors R13, R14, the same voltage wou1d be present at the loop resistors R3, R4, when the subscriber loop is open as well as closed, which could prevent evaluation of the loop. With in-creasing ratio of the resistance values o~ the inverter resistors R13~ R14 to those of ~he loop resistors R3, R4, the evaluation threshold for the loop signals also increases.
The amplifier J6 has a ga~n 1 and serves for inverting the signals coming from the preceding amplifier J4 and J~, respect-ively, for modulating the voice wire B.
-- llllS86 In order to achleve a large hybrtd attenuation if the subscriber loop is open, the differential amplifier J3 is driven into limit-ing via the transistor T by the loop signal at the point S, so that no a-c voltage can reach the point G of the outgoing branch of the hybridO
As a~orementioned, two circuit variants or embodiments of the hybrld arrangement are shown in the figure, both of which are described hereinafter in greater detail.
The first circuit variant has a real lnput resistance and there-~ore a real internal generator resistance and a complex line balanclng network whereby me;.sured transn~ssion values are obtained which correspond to conventional inductive hybrids.
The second circuit varlant is equipped with a complex input im-ped~nce and, consequently, with a complex internal generator im-pedance and with a complex line balancing network. The dimenslon-ing of the balancing networks depends upon the type of cable of the subscriber loop and.upon the internal impedence of the sub-scriber station.
In the embodiment of the circuit which has a real input resistance R15, the latter is connected between the polnts 1-1. The connection o~ the points 2-3 is severed and connectlon of the points 2-4 is maintained; tn the practical design of the circuit, the ampli~ier J5 and the llne balancing network N2 as well as the unidentifted resistor and capacitor associated there~th, are omitted~ The voltage present at the real input resistor R15 is transmitted via the differential amplifier J3 to the outgoing branch of the hybrid arrangement, point G.
The voltage present in the incoming direction at the point K is transmltted v~a the modulation circuit to the voice wires A, B
s~
1~11S86 and therefore, ~lso to thq inpuls of the differential amplifierJ30 In order to obtain ~ larg~e hybrid attenuation, a counter-voltage is applied to t.he inv~ ted input of the di~ferential amplifier J3 by the amplifier J51, so that there ls no voltage at the point G.
Under operating conditions iOe. lf the voltage present at the point K produces a ~requency-dependent voltage on the voice wires A, B, the ~requency response o~ the line balancing network N
must correspond to that of the external termination o~ the voice wires A, Bo Since the input resistance R15 together with the capacitor Cl is also frequency-dependent to a certain extent, the line balancing network N is shunted by an R-C member, the elec-trical data or values Or which correspond to those of the input resistance R15 and the capacitor Cl~
In the embodiment of the circuit which has a complex input im-pedance, a complex ~nput impedance Nl is connected between the polnts l-lo Connection of the points 2-3 is maintained and that of the points 2-4 is severed; the amplifier J51, the complex balancing network N with the R-C component thereof and the other-wise unidentified resistor associated therewith being omitted in the practical construction of the circuit. The circuit arrange-ment is formed in such a manner that the voltage at the voice wires A, B is transmitted as an unbalanced or asymmetric voltage to the point G o~ the outgo~ng branch of the hybrid via the dif~erential amplifier J3. An unbalanced or asymmetric voltage at the point K of the incoming branch is transmitte~ to the YoiCe wires A, B as a balanced or symmetric voltageO The frequency response of the complex input ir..pedance Nl, as well as the llne balancing network N2 for the co~plex internal generator impe~ance corresponds to the load on the voice wires A, Bo . -8-llllS86 The current flowing in the line balancing network N2 is converted by tne amplifier J5 into a control voltage for the current generators. The current delivered by the current generators to the parallel circuit consisting of the complex input impedance Nl and the subscriber stat~on consequently has the same frequency response as the current in the line balanc~ng network N2. Through appropriate selection of the gain of the operational amplifiers Jl, on the one hand, and J2 and J5, on the other hand, the voltage of the voice wires A, B is exactly equal to the voltage at the point K. The equality of these voltages ls utilized for the hybrid function of the arrangement. Wlth equal hybrld re-sistances R16 to ~21, the voltage at the point K is fed vla the amplifier J4 to the resistor R17 and counteracts with twice the amplitude the voltage from the voice wire A, which is thereby cancelled. Together with the voltage of the voice wire B, a common-mode signal is delivered therewith to the inputs of the differential amplifier J3 but is not taken into consideration.
The advantage of the last-described circuit variant is that the input impedance is matched to the impedance of the connected line. A telephone system constructed in this manner is very well matched to a line network. If, in additlon, the input impedance and the lnternal impedance of the subscriber station are matched to the line impedance, then good hybrid attenuation and side-tone reduction, respectively, can be obtained also with very short loops or connected linesO
The use of operat~onal amplifiers affords the realization o~
the balancing network N2 with physical or spatially small components, which have an impedance that is many times higher than that of conventional balancing networks.
_9_
Claims (9)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. In a circuit arrangement for an electronic subscriber feed with loop current supervision, ringing connection and hybrid for a transition from two to four-wire operation with mutually symmetrically connected current generators for communication facilities such as branch telephone exchanges, the current generators comprising, in a two-wire branch of the hybrid, operational amplifiers having respective transistors operatively connected therewith, said operational amplifiers being operative as pure voltage followers and having inverted inputs through which modulation of the loop current is controllable, dynamic self-balancing of said current generators being increased by amplification of a modulation voltage applied to said two-wire branch in an incoming line branch of a four-wire branch of the hybrid, a differential amplifier operatively connected with said operational amplifiers and having an output connected to an outgoing line of said four-wire branch and an input, a transistor having a collector connected to said input of said differential amplifier, and means for applying, with the loop open, a loop signal through said transistor connected to said input of said differential amplifier for controlling said differential amplifier so as to obtain a large hybrid attenuation in a manner that no a-c voltage reaches said output of said differential amplifier, said hybrid comprising a complex line balancing network connected in said four-wire branch and an input impedance connected in said two-wire branch, said input impedance being selected from a group consisting of a real resistance and a complex impedance.
2. Circuit arrangement according to claim 1 wherein said input of said differential amplifier is inverted, and including an amplifier operatively connected to an output of said differential amplifier for applying a countervoltage to said inverted input of said differential amplifier, with the loop closed, for opposing a four-wire send voltage and so as to obtain a large hybrid attenuation.
3. Circuit arrangement according to claim 2 including voice wires operatively connected in said two-wire branch to inputs of said operational amplifiers and having an external termination, said complex line balancing network having a frequency response corresponding to the frequency response of said external termination of said voice wires.
4. Circuit arrangement according to claim 2 including an R-C
component connected in shunt with said complex line balancing network.
component connected in shunt with said complex line balancing network.
5. Circuit arrangement according to claim 2 including voice wires connected in said two-wire branch to inputs of said oper-ational amplifiers and having a load connected thereto, said complex input impedance and said complex line balancing network having a frequency response corresponding to the load connected to said voice wires.
6. Circuit arrangement according to claim 5 including an in-coming line branch of said four-wire branch connected to the input of said operational amplifiers, and means cooperating with said operational amplifiers for converting an unbalanced input voltage applied to said incoming line branch to a balanced voltage at said voice wires.
7. Circuit arrangement according to claim 1 including means for evaluating the loop comprising resistances connected to outputs of said operational amplifiers.
8. Circuit arrangement according to claim 1 including voice wires connected in said two-wire branch to inputs of said oper-ational amplifiers, and balancing resistors respectively connected operatively to said operational amplifiers and directly to said voice wires.
9. Circuit arrangement according to claim 1 including a complex input resistance connected in said two-wire branch, and a complex line balancing network in said four-wire branch.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19762655005 DE2655005C3 (en) | 1976-12-02 | 1976-12-02 | Circuit arrangement for an electronic subscriber feed |
| DEP2655005 | 1976-12-02 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1111586A true CA1111586A (en) | 1981-10-27 |
Family
ID=5994663
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA292,254A Expired CA1111586A (en) | 1976-12-02 | 1977-12-02 | Circuit for electronic subscriber feed |
Country Status (13)
| Country | Link |
|---|---|
| AT (1) | AT363523B (en) |
| BE (1) | BE861297A (en) |
| CA (1) | CA1111586A (en) |
| CH (1) | CH630209A5 (en) |
| DE (1) | DE2655005C3 (en) |
| DK (1) | DK533777A (en) |
| FR (1) | FR2373201A1 (en) |
| GB (1) | GB1587868A (en) |
| IE (1) | IE45750B1 (en) |
| IT (1) | IT1088708B (en) |
| LU (1) | LU78546A1 (en) |
| NL (1) | NL7713305A (en) |
| SE (1) | SE7713728L (en) |
Families Citing this family (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4203009A (en) * | 1977-08-17 | 1980-05-13 | The Post Office | Unbalanced/balanced converter circuits |
| NL7810086A (en) * | 1978-10-06 | 1980-04-09 | Philips Nv | POWER BRIDGE FOR A SUBSCRIBER FLOW. |
| DE3014187C2 (en) * | 1980-04-14 | 1983-11-17 | Nixdorf Computer Ag, 4790 Paderborn | Circuit arrangement for the two-wire connection of a telephone subscriber to one line each for incoming and incoming signals |
| DE3032970A1 (en) * | 1980-09-02 | 1982-04-15 | Telefonbau Und Normalzeit Gmbh, 6000 Frankfurt | Balanced signal derived from telephone line - has operational amplifier between constant current generators with input connection to potential divider |
| DE3116783C2 (en) * | 1981-04-28 | 1983-09-01 | Standard Elektrik Lorenz Ag, 7000 Stuttgart | Circuit arrangement for a subscriber line circuit for telephone systems |
| US4431868A (en) * | 1981-07-09 | 1984-02-14 | International Telephone And Telegraph Corporation | Solid state telephone line interface circuit with ringing capability |
| DE3138726A1 (en) * | 1981-09-29 | 1983-04-07 | Siemens AG, 1000 Berlin und 8000 München | Subscriber connection circuit for connecting two-wire subscriber connection lines to a four-wire through-connecting digital time division multiplex exchange |
| DE3214624C2 (en) * | 1982-04-20 | 1986-05-28 | Siemens AG, 1000 Berlin und 8000 München | Circuit arrangement for evaluating subscriber loop states in telephone systems, in particular in telephone branch exchange systems |
| BR8401869A (en) * | 1984-04-23 | 1985-11-26 | Microlab Sa | VOICE FREQUENCY REPEATER |
| FR2564678B1 (en) * | 1984-05-18 | 1986-09-12 | Thomson Csf Mat Tel | SUBSCRIBER CIRCUIT LINK INTERFACE FOR TELEPHONE SWITCH |
| DE4306251C1 (en) * | 1993-03-01 | 1994-06-01 | Bosch Telecom | Telecommunication system user connection line circuitry - indicates status of telephone user connection line according to call signal which switches transistor connected to operational amplifier inputs |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CH586983A5 (en) * | 1974-12-23 | 1977-04-15 | Ibm | |
| DE2556157C3 (en) * | 1975-12-11 | 1979-01-18 | Deutsche Telephonwerke Und Kabelindustrie Ag, 1000 Berlin | Circuit arrangement for an electronic subscriber feed |
-
1976
- 1976-12-02 DE DE19762655005 patent/DE2655005C3/en not_active Expired
-
1977
- 1977-11-18 LU LU78546A patent/LU78546A1/xx unknown
- 1977-11-24 CH CH1455077A patent/CH630209A5/en not_active IP Right Cessation
- 1977-11-29 BE BE183007A patent/BE861297A/en unknown
- 1977-11-30 IE IE242877A patent/IE45750B1/en unknown
- 1977-11-30 FR FR7736123A patent/FR2373201A1/en not_active Withdrawn
- 1977-12-01 AT AT0860777A patent/AT363523B/en not_active IP Right Cessation
- 1977-12-01 IT IT3024377A patent/IT1088708B/en active
- 1977-12-01 NL NL7713305A patent/NL7713305A/en not_active Application Discontinuation
- 1977-12-01 DK DK533777A patent/DK533777A/en not_active Application Discontinuation
- 1977-12-01 GB GB5018377A patent/GB1587868A/en not_active Expired
- 1977-12-02 CA CA292,254A patent/CA1111586A/en not_active Expired
- 1977-12-02 SE SE7713728A patent/SE7713728L/en not_active Application Discontinuation
Also Published As
| Publication number | Publication date |
|---|---|
| DK533777A (en) | 1978-06-03 |
| IE45750B1 (en) | 1982-11-17 |
| BE861297A (en) | 1978-03-16 |
| SE7713728L (en) | 1978-06-03 |
| GB1587868A (en) | 1981-04-08 |
| DE2655005A1 (en) | 1978-06-15 |
| LU78546A1 (en) | 1978-04-13 |
| DE2655005B2 (en) | 1979-08-09 |
| IT1088708B (en) | 1985-06-10 |
| AT363523B (en) | 1981-08-10 |
| ATA860777A (en) | 1981-01-15 |
| CH630209A5 (en) | 1982-05-28 |
| DE2655005C3 (en) | 1980-04-17 |
| IE45750L (en) | 1978-06-02 |
| FR2373201A1 (en) | 1978-06-30 |
| NL7713305A (en) | 1978-06-06 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CA1096522A (en) | Subscriber line-trunk circuit | |
| US3855430A (en) | Electronic hybrid circuit for two-wire to four-wire interconnection | |
| CA1111586A (en) | Circuit for electronic subscriber feed | |
| CA1047659A (en) | Active hybrid circuit | |
| US3975594A (en) | Apparatus utilizing a phantom circuit for connecting additional subscribers to a telecommunication system | |
| US3909559A (en) | Electronic hybrid | |
| US3955052A (en) | Subscriber unit particularly useful for time-division-multiplex system | |
| US2829203A (en) | Electronic telephone subscriber's line circuit for neutralizing the effects of longitudinal induction and longitudinal unbalance | |
| US2288049A (en) | Telephone set circuit | |
| US4538032A (en) | Interface circuit with impedance adaptation means | |
| US3823273A (en) | Subscriber's telephone circuit | |
| US3843844A (en) | Subscriber loop circuit apparatus | |
| CA1206646A (en) | Loop-circuit for telephone line | |
| US4485277A (en) | Apparatus for transmitting and/or receiving balanced signals on a two-wire telecommunication line | |
| US3932712A (en) | Telephone transmission system | |
| US3617645A (en) | Signaling circuit with audible noise reduction | |
| US3689700A (en) | Subscriber loop extension unit | |
| US3904838A (en) | Two-wire, bi-directional voice frequency repeater | |
| JPS6342977B2 (en) | ||
| JPS6256691B2 (en) | ||
| US2488577A (en) | Arrangement for limiting noise interference in carrier telephone systems | |
| CA1181186A (en) | Transformerless hybrid circuits | |
| US1045600A (en) | Telephone transmission system. | |
| US4682356A (en) | Apparatus for transmitting and/or receiving balanced signals on a two-wire telecommunication line | |
| US4897871A (en) | Apparatus for transmitting and/or receiving balanced signals on a two-wire telecommunication line |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |