DE3225635C2 - Subscriber connection circuit with high-resistance switchable supply circuit and an indication circuit carrying out various indications - Google Patents

Abstract

In order to increase the evaluation reliability of the indication circuit, when the operating state changes to and from the "ringing phase" operating state, the setting commands are only executed when the alternating ringing voltage has a zero gear. During the transition to the "ringing phase" operating state, the "ringing pause" operating state is set as the intermediate state, in which the indication circuit is already prepared for the "ringing phase" operating state.

Description

The invention relates to a subscriber line circuit for the office-side connection of a subscriber line with switching devices for high resistance of the supply circuit, with switching devices for ringing current feed, as well as with one by evaluating the potential state on cable cores-related fixed Coupling points several different indications performing indication circuit, with the corresponding each different response thresholds are effectively switched, the switching means for High-resistance switching of the supply circuit and for ringing current feed when setting four different ones Operating states can be controlled independently of one another.

Compared to a known subscriber line circuit (DE-OS 29 38 998), in which only three different Operating states are possible by making the call phase and the call pause a single operating state form, there are advantages with regard to the indication of the loop key as a result of a call.

The setting commands for the aforementioned settings of the operating states are used in such a subscriber line circuit supplied by a central control in the form of a computer, by which also specified which threshold value in each case for the indication circuit On the other hand, the ones determined by the indication switching influence Line statuses the formation or delivery as well as the execution of the mentioned setting commands. Both said switching means for high-resistance switching of the feed circuit or for ringing current feed it is a relay.

The control of the relay in such a way that, according to a proposed solution, four distinguishable operating states are possible, in contrast to known solutions, between an operating state "call phase" and a distinction is made between an operating state “call pause”, increases the reliability of the evaluation in the call operation, which is of interest because a call occurs during a Rufstromeinspeisung The loop closure of the subscriber line must be recognized as quickly and reliably as possible to be able to quickly switch off the call, otherwise the subscriber station lifted the receiver Call current flowing through the microphone circuit could lead to destruction.

The last-mentioned requirement for the possibility of faster call deactivation also applies here. About that In addition, the switching of the relay contacts should be non-destructive, as well as undefined settings.

conditions or transitions should not be able to occur, as this results in asymmetries on the subscriber line. Finally, it must be avoided that the indication circuit when changing from an operating state in another gives off impulses.

The invention is therefore based on the object of specifying a subscriber line circuit in which the switching of the relay contacts is non-destructive and takes place in such a way that no undefined settings or transitions occur and thus ultimately no false displays occur due to the indication switching.

This object is achieved with a subscriber line circuit of the type mentioned at the outset, which is implemented according to the invention is characterized by a control circuit for said switching means, by means of which Activation in such a way that they change status when Bcii iebs / between the operating states »idle«, »call recording« and »pause« immediately after occurrence of the corresponding setting commands supplied by a central control, the dem Assume the appropriate combination of switch positions in the following operating state, with Transitions to and from the operating state

»Call phase«, however, only adopt the corresponding combination of switch positions when the next one processing-synchronous zero crossing of the alternating ringing voltage is present, with the transition to the "Call phase" operating state, provided it has not already started from the "Call pause" operating state, initially the combination of switch positions corresponding to the »call pause« operating state as an intermediate state is taken, in which, however, the response threshold corresponding to the "ringing phase" operating state the indication circuit is activated, and that the assumed as an intermediate state "Call pause" operating state regardless of an existing setting command for the operating state "Call phase" is retained or assumed from the "Call phase" operating state if from the indication circuit, the creation of a loop closure at the subscriber line is shown.

In the subscriber line circuit according to the invention, all of the above-mentioned requirements are met fulfills what can be seen from the following description of an exemplary embodiment of the invention shows, in which reference is made to a figure.

As the figure shows, the circuit arrangement according to the invention contains resistors R 1 to R 3, via which one wire, the a wire of a subscriber line TL, is connected to one pole (- Ub) of a supply voltage source, and resistors R 4 and R 5 via which the other wire, the δ-wire of the subscriber connection line, is connected to the other pole (earth) of the voltage source. The resistors R 2 and R 3 can be bridged by a contact ka of a relay A, the resistor R 5 can be bridged by a contact kb of a relay B. Depending on the switching position of the contacts mentioned, the wires of the subscriber line can be connected to the supply voltage source with high or low resistance. It can thus be ensured that the supply current source, which serves several subscriber connection circuits, is not overloaded, since the maximum supply current is not consumed in all operating states. It can also be prevented that an excessively long operation of the earth key in the subscriber set leads to an overload of the switching elements in the supply circuit, since in such a case a switch is made from a low-resistance supply to the high-resistance supply.

The circuit arrangement shown also shows a relay R with a contact kr, via which a ringing current feed between the feed resistors R 2 and R 3 on the subscriber line is possible.

There is also an indication circuit K available, which is connected to line-related fixed coupling points of the subscriber line circuit, and which is used to carry out different indications, for. B. the incentive indication and the indication of the closure of the loop as a result of a call and during the election. In order to do justice to the current conditions at the time of making these indications, which may not be the same, and the different requirements for the evaluation speed, different response switching thresholds can be effectively switched with this indication switching depending on the type of indication to be carried out. A filter element, not shown here, which is connected to the indication circuit for certain indications, also ensures an increase in the evaluation reliability.

In connection with the present invention of particular interest, the circuit arrangement shown has a control circuit Srauf, which is used to set the Reiais A, B and R and which serves several such subscriber connection circuits a memory Sp are supplied, furthermore a signal supplied by the indication circuit when a loop is established and a signal supplied by a synchronization circuit S which coincides with the zero crossings of the alternating ringing voltage or preferably with switching times that are around the response time of the relay R before these zero crossings .

The control circuit Sr contains a logic circuit V, the first input / 1 of which is supplied with the signals supplied by the indication circuit K and the two further inputs / 3 and / 4 of which are the two-bit digital setting commands accepted by the memory SP. It contains two NOR elements N 1 and / V 2 and a NAND element / V3. The inputs of the NOR element NX are connected to the aforementioned inputs / 3 and / 4. The output of this NOR element NX is connected to one input of the NOR element Λ / 2, the other two inputs of which are connected to input IX in one case and to input / 4 of the logic circuit in the other. One input of the NAND element N3 is also connected to the output of the NOR element NX , its other input, which is a negating input, is connected to an input / 2 of the logic circuit, which will be discussed below. From the output of the NAND element N3 , a connection leads to an output £ 1 of the logic circuit V or to a register Reg 1, which is also acted upon at an input T by clock pulses which occur with a period of 500 \ is , for example. The output of the NOR element Λ / 2 leads to an output £ 2 of the logic circuit or to a buffer ZS, which is also acted upon at an input T by the aforementioned clock signals.

The intermediate memory ZS is followed by a register Reg 2 , which takes over the information contained in the intermediate memory ZS when a signal supplied by a synchronization circuit S occurs.

The output of the register Reg 1 is connected on the one hand to the control input of the relay B and on the other hand to the non-inverting input of a logic element U. The output of register Reg2 is connected to the control input of relay R, to the negating input of said logic element LJ and to input / 2 of logic circuit V. The output of the logic element U is connected to the control input of the relay A.
The mode of operation of the arrangement shown is explained in more detail below.

It is assumed here that the following meaning is assigned to the bit combinations of the setting commands supplied by the central control and arriving at inputs / 3 and / 4 of the logic circuit: Operating state »Idle« / 3 = 0, / 4 = 1; Operating status »ringing phase« / 3 = 1, / 4 = 0; Operating status »pause« / 3 = 1./4 = 1.
It is initially assumed that the

if "idle" is present, which means that none of the relays A, B and R has picked up.

If now a single command for the establishment of the operating state »conversation / dial recording« occurs in the form of the bit combination / 3 = 0, / 4 = 1, this leads to the appearance of a signal corresponding to the binary value 1 at output E 1 of the logic circuit V, which is transmitted via the Register Reg 1 to the control input of relay B, the contact of which is then closed,

the potential, so that with the subsequent zero crossing of the alternating ringing voltage, the relay R drops and the relay A picks up. The Bc-15 operating state "pause" is thus established, so that the call is switched off without waiting for the corresponding setting command. This intermediate status »call pause« is retained until the operating status is subsequently activated by the central controller

quick call disconnection is taken into account.

If one of the Be-25 If the instinctual states "rest", "pause" or "conversation / dialing" are to be established, then this happens this with a delay until the next zero crossing of the alternating ringing voltage without how previously described, an intermediate state »pause«

the setting delay does not affect the indication circuit, i.e. immediately when the final one occurs Operating state is set accordingly and that missing pulses when transitioning from the intermediate state »Call pause« for the operating state »Call phase« cannot occur.

If the indication circuit K reports a loop closure of the subscriber line during the "ringing phase" operating state, then has

and at the one input of the logic circuit this a U at the output £ "2 of the logic circuit arrives. The output E 2 of the logic circuit potential change to which the binary value 0 corresponds to V continues to supply, as in the preceding
"Idle" operating state, a signal corresponding to the binary value 0, so that the buffer and the
connected registers Reg 2 each retain their output signal of the binary value 0 unchanged with the
As a result, on the one hand, the relay R is not energized
State remains, on the other hand because of the negated
Input the link condition of the logic element U is met. This means that 20 "interviews / voting" are also ordered. Relay B is thus also relay A picks up, so that the low resistance of the supply circuit provided for the above-mentioned requirement for a possible operating state "conversation / dial recording" is established
immediately after occurrence of the mentioned setting command.

If a setting command for the establishment of the operating state is issued from the »idle« operating state "Call phase" occurs in the form of the bit combination / 3 = 1, / 4 = 0, then the following processes take place: Da an

all inputs of the NOR gate N2 the binary 30 is taken. Because there is a potential corresponding to the intermediate storage value 0, a signal corresponding to the binary value 1 occurs at the output of the due to the relevant setting command change £ 2, which first reaches the intermediate memory ZS at output E2 of the logic circuit Kauftre, but the signal in the intermediate memory ZS and the first takeover in the register Reg 2 the following from the synchro delayed acquisition in the register Organization circuit S delivered stimulus, await 35 Reg 2 is namely must th from the register Reg 2 forth first, and therefore the relay R not affect an unchanged the binary value 1 corresponding PO can . At the non-inverting input of the NAND potential value at the input / 2 of the logic circuit element N3, a signal corresponding to the binary value 0, such as the NAND element N 3 , arrives from the output of the NOR element V and thus to the negating input of the Ni placed, so that despite a new that at the output Ei of the logic circuit a 40 setting command at the inputs / 3 and / 4, the control signal of the binary value 1 occurs, which via the register ersignale the binary value 0 for the relay A and the Reg 1 without delay to the control input of relay B binary value 1 for the B are maintained,
arrives and makes it tighten. Because of this, arc discharges when opening the Rc-

Negation of unchanged the binary value relay contacts 0 correspond avoided, their lifespan increased sponding tab Reg2 standing signal by the 45 also can not be interference injection into the Steueinen input of gate U is also erlogik and come to the occurrence of missing pulses, the relay A at. In a manner not shown, the evaluation circuit also evaluates
which the mentioned filter element of the evaluation circuit K
is placed in the active state corresponding to the operating state »call pause«, so that a total of this loading 50
operating state »pause« is set as an intermediate state.

This intermediate state is used to effectively switch the threshold value corresponding to the “ringing phase” operating state in the evaluation circuit K. With the occurrence of the next zero crossing of the ringing alternating voltage or a time preceding the response time of the relay R , the synchronization circuit 5 emits a signal which causes the signal stored in the intermediate register ZS to be transferred to the register Reg 2 , with the result that Now, that is, exactly at the zero crossing of the ringing alternating voltage, the relay R picks up and the relay A drops out, whereby the setting conditions corresponding to the operating state "ringing phase" are present. 65

The setting sequence described ensures that switching off the relay contacts is non-destructive takes place, on the other hand it is ensured that

1 sheet of drawings

Claims (2)

Patent claims: 1. Subscriber line circuit for the office-side connection of a subscriber line (a, b) with switching means (A k, a; B, k, b) for high-resistance switching of the feed circuit (Al - RS), with switching means (R, kr) for ringing current feed, as well as with a By evaluating the potential state at fixed coupling points related to the line wires, several different indication circuits (K) carrying out different indications, in which different response thresholds are activated accordingly, the switching means for switching the feed circuit to high resistance and for ringing current feed being controlled independently of one another when four different operating states are set, characterized by a control circuit (ST) for said switching means, by means of which they are controlled in such a way that they correspond to changes in operating status between the operating states "rest", "conversation / dialing" and "pause" immediately after occurrence of the the setting commands supplied by a central controller, which assume the combination of switching positions corresponding to the respective subsequent operating state, but only adopt the corresponding combination of switching positions during transitions to or from the »ringing phase« operating state when the next zero crossing of the ringing voltage, synchronized with the processing cycle, is present, with Transition to the "ringing phase" operating state, provided that it is not already carried out from the "ringing pause" operating state, first the combination of switch positions corresponding to the "ringing pause" operating state is assumed as an intermediate state, but in which the response threshold corresponding to the "ringing phase" operating state is already adopted Indicator circuit (K) is activated, and that the operating state assumed as an intermediate state »Call pause« is retained regardless of an existing setting command for the operating state »Call phase« or from the operating state »Call phase« Ehend is taken when the indication circuit (K) indicates the establishment of a loop connection at the subscriber line. 2. Subscriber circuit according to claim 1, characterized by a circuit arrangement (S) which derives a processing-clock-synchronous trigger signal for the control circuit (ST) from the ringing alternating voltage supplied to it, which has a lead time compared to the zero crossings of the ringing alternating voltage, which is used for the switching time of the ringing current feed Call relay (R) is the same.