DE2547880A1 - CIRCUIT ARRANGEMENT FOR DETECTING OPERATING CONDITIONS OF A SUBSCRIBER LINE AND FOR CALLING AND CALLING DISCONNECTING IN TELEPHONE SWITCHING SYSTEMS - Google Patents

Description

STANDARD ELECTRICS LORENZ
SHARED COMPANY

Stuttgart

G.Fink-W. Room 2-1

Circuit arrangement for the detection of operating states of a subscriber line and for call connection and call disconnection in telephone exchanges.

The invention relates to a circuit arrangement for recognizing the operating states of a subscriber line and for connecting calls as well as disabling calls in telephone exchanges, with indicators for recognizing the loop closure status, pressing the earth button and lifting the handset of the called party, these indicators showing their switching states report to a central control device and the indicator for detecting the earth button pressure to that feed resistor is connected, which belongs to the speech wire that can be connected to earth with the earth button, and from the central control device controlled means for call connection, which has a call generator in series with the supply current source to the subscriber line place.

In such known telephone systems, three indicators are usually used to identify the operating states a subscriber line is used, namely an indicator corresponding to the so-called Α relay for recognizing the loop closure state, an indicator corresponding to the so-called X-relay for recognizing the earth key pressure and a so-called

10/22/1975
Krü / Mr

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Y-relay corresponding indicator for the detection of the loop closure in the ringing state that causes the ringing to be switched off.

From the magazine "SEG-Nachrichten ¹¹ , 1957, Issue 2, pp.76-78, it is known to use an additional gate for the transmission of a high call power in the subscribers to connect the usual 50 Hz call signal when the transmission of this call power over the electronic coupling network is not possible A magnetic amplifier is used as a gate in the subscriber circuit.

From the German patent specification 1 919 585 it is also known during the call state, the subscriber line leading to the called party with an indicator for recognizing the loop closure state and to couple a central call generator and to alternately switch the indicator and the call generator into effect. Only the loop closure is recognized in the phase in which the call generator is not activated. This can result in a delay in the loop closure detection and the call disconnection.

The object of the invention is to provide a circuit arrangement of the type mentioned in which only two indicators are needed for the tasks mentioned. This is characterized by the features characterized in claim 1 achieved. With the indicator for the detection of the loop closure, the lifting of the is also possible during the call status Handset immediately recognizable by the called party.

The invention will now be explained in more detail using an exemplary embodiment.

The embodiment in the figure represents part of a subscriber circuit. The speech wire a of a subscriber

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Line is connected to the negative pole -U of a supply current source via the rest side of a changeover contact rl, a part of the winding of a line transformer-Lü and a feed resistor Wl, while the speech wire b of the subscriber line is connected to the rest side of a changeover contact r2, a second part of the winding of the Lei processing unit Lü and another feed resistor Wl ^{1 is} connected to the grounded pole of the feed current source e. The changeover contacts rl, r2 belong to a call switch relay R. The two partial windings of the line transformer Lü are directly coupled by a capacitor C. Another winding of the line transformer Lü is connected via an output Ka, Kb to the cfen coupling network, which may be formed from electronic coupling elements. A resistor bridge composed of mutually identical resistors LJ2, W2 ¹ and mutually identical Vlideristors i / 3, W3 ^{1 is} connected to the two supply resistors Ul, VJl ^{1 of the same value.} In the diagonal branch of this resistance bridge there is an indicator II with its two input terminals, the output of which is led to a central control device ST. A further indicator 12 is coupled to the supply resistor Wl ″, the output i2 of which also leads to the central control device ST. These two indicators are preferably equipped with operational amplifiers. The indicators II, 12 can have certain threshold values in a manner not shown.

Between the rest spring of the Urnschal tkontakts rl and the reference potential leading connection of the supply current source is the Series connection of a call generator G and the supply current source U can be switched on via a control connection g of the central control device ST. Between the spring of rest of the

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switching contact r2 and the reference potential leading connection there is a parallel connection of a resistor W4 a capacitor Cl and a diode Dl. The line-side This parallel circuit is connected via a diode D2 and a resistor W8 to the positive input terminal of the indicator Il connected.

The Rufanschalterelais R is in the collector circuit of an npn transistor T. A voltage source + U serves as the supply voltage for the transistor stage. A diode D3 is connected in anti-parallel to the base-emitter path of this transistor. The base of the transistor T is connected to the tap of a voltage divider consisting of two resistors U5, Ά6, which is arranged between a terminal carrying negative potential -U and a control terminal h of the central control device ST. For ones *! Tunq the call switching relay R can be supplied to the control terminal of h positive potential tap of the uar Spannunqsteilers il is further connected via a Viiderstand W7 and a Zener diode Z to the output.

In the following, the mode of action of the will now be described Circuit arrangement explained.

1. Idle state

When the line a, b is in the idle state, the Rufanschalterelais R is switched off, via the resistors Ul, Wl ¹ , the supply voltage is offered between the speech wires a, b. There is no feed current. The thresholds at the inputs of the indicators (operational amplifiers) II, 12 are chosen so that the outputs il, i2 have reference potential in this state.

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2. Loop closed state

After lifting the handset, feed current flows in the subscriber line loop. As a result, the potentials at the input connections of the indicators II, 12 are shifted in such a way that these indicators switch to the on-state; For example, they emit potentials of -33V as 1 signals at the outputs il, i2.

3. Earth button press state -

If the subscriber presses his earth button, a current flows from the earth applied to the speech wires a, b via the speech wire a and the resistor ill, while the resistor Wl ^{1 is} short-circuited. "As a result, the indicator 12 / when ii: i conversation state switches to the idle state, so that reference potential occurs at its output il, while the indicator II remains in its on-state when the line loop is closed or responds when the line loop is open. The information whether the earth button actuation from the state "line loop closed" or "line loop open" results from the logical connection and the respective operating state of the subscriber line before the earth button is pressed ST, which then initiates a query in accordance with the "line loop closed" status or recognizes the partial operator station as having priority in accordance with the "line loop open" status and controls the further process accordingly.

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4. Call status

To establish the call state, the central control device ST applies positive potential to the control connection h. This results in a positive potential at the base of the transistor T. The transistor T is switched through and allows the Rufanschalterelais R to respond. The switching contacts rl, r2 switch over. A ringing current flows from the call generator G via the changeover contact rl, the speech wire a, the not shown alarm clock of the Tei Inehrnerstation ^ the speech wire b, the Ur.ischal tkontakt r2, the capacitor Cl, earth and the supply current source U to the call generator G back. The Hecker rings the bell, but no direct current is flowing yet. The capacitor C1 has a negative potential. Positive peaks of the ringing voltage are diverted via the diode 31. Since the line-side connections of the line transformer Lü are open, the potential at the common connection point of the resistors W2 ¹ , W3 has a high negative value. This potential is more negative than that of the capacitor Cl, so that the diode D2 is blocked. The indicators II, 12 are in the idle state and therefore emit reference potential at their outputs il, i2. Therefore, the Zener diode Z is blocked.

See loop closure status during ringing current injection

If the subscriber picks up his handset during the call, a direct current superimposed on the alternating current flows

in the line loop. This direct current creates resistance
if W4 was a> voltage drop of such a level that the diode D2 becomes conductive. As a result, the potential at the input of the indicator II shifts in such a way that it switches to the on- state and thus negative potential (-33V)

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at its exit il lays. As a result, the Zener diode Z becomes conductive in the Zener region, so that the potential at the base of the transistor T falls to a negative value limited by the diode D3. The transistor T is thus blocked and lets the Rufansehalterelais R drop out. During the switching back of the switching contacts rl, r2, the charging of the capacitor Cl causes the maintenance of the on-switching state of the indicator II. If the shutdown process is ended, the loop current then flowing takes over the maintenance of the on-switching state of the indicator II, so that the call pause relay R remains forcibly switched off. The central control device ST also recognizes the switched-on state of the indicator II and switches off the positive potential at the control terminal h. As soon as the switching back of the switchover contacts rl _a r2 has ended, the loop closure state described in section 2 is reached.

6. Electoral state

Through the expiry of the number switch in the participant's division the supply current is interrupted periodically. The indicators II, 12 recognize the idle state and during the dialing pulse during the break after a dialing pulse, the loop closure-r State. The adding up of the individual dialing pulses to the dialed digit is carried out in the central control device ST made in a manner not shown. Through centralization the summing circuit in the control device a conversion of the circuit arrangement shown is not necessary if instead of one that works with a number switch Subscriber station a subscriber station operating according to the multi-frequency code dialing method is used.

2 claims

1 sheet of drawing with 1 figure

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Claims (2)

G.Fink-W. Room 2-1
Claims ti) Circuit arrangement for recognizing the operating states of a subscriber line and for connecting and disabling calls in telephone exchanges, with indicators for recognizing the loop state of pressing the earth key and lifting the handset of the called party, these indicators reporting their switching states to a central control device and the indicator for recognizing the earth key press is connected to that feed resistor that belongs to the speech wire that can be connected to earth with the earth button, and with means for call connection controlled by the central control device, which connect a call generator in series with the supply current source to the subscriber line, characterized in that the speech wires (a , b) Changeover contacts (rl, r2) of a call switching relay (R) are inserted, that ^x -aie working side of one changeover contact s- (rl) the call generator (G) can be connected, that between the working spring of the other changeover contact ( r2) un d a connection leading to reference potential is a parallel RC element (W4, Cl), that the contact-side connection of this RC element is connected via a diode (D2) to the input of the indicator (II) provided for loop detection and that the output of this Indicator is coupled to the control circuit of the Rufansehalterelais that when a signal corresponding to the loop closure occurs at the output of this indicator, the Rufanschaltbefehl is suppressed. 2. Circuit arrangement according to claim 1, characterized in that a transistor holding stage (T) controlling the Rufanschalterelais is provided, in the base circuit of which the output signal of the indicator (II) for loop detection via a Zener diode (Z) is fed as reverse voltage. 709818/0880