DE3400304A1 - Circuit for identifying a loop condition - Google Patents

Abstract

Circuit for identifying a loop condition in a telephone device which signals this condition by forwarding the loop closure to a telephone line from which power is supplied to the circuit, in particular for triggering functions within the telephone device, with an active three-pole switch which is inserted between the connected telephone set and a first line wire, an active three-pole switch being assigned to only one of the telephone sets in the case of a telephone device with at least one further connected telephone set, while a winding of a relay assigned to this telephone set is inserted in the DC circuit of the other connected telephone set, and the response speed of the active three-pole switch is selected as higher than that of the assigned relay.

Description

description

The invention relates to a circuit arrangement according to the main patent ... (patent application P 32 45 839.8).

The circuit according to the main patent is used in particular as an assembly in a telephone device which enables the parallel connection of two telephone sets to an exchange line with a common number.

This facility is intended to ensure that when telephones are used, not through additional hook switches etc. for the parallel connection of telephones are specially equipped, it is prevented that both apparatuses at the same time connected to the line, thus maintaining the confidentiality of a conversation cannot be affected.

In the circuit arrangement according to the main patent, the function is Telephone equipment even with reverse polarity and compliance with narrow limits the increase in the DC resistance in the stimulus state is ensured.

As through within the switching facilities of the exchange network Any improvements achieved, an increase in the incentive resistance can be accepted can, the invention specified in claim 1 is based on the object of a simplified Specify circuit arrangement which works safely despite the simplification and In particular, the simultaneous connection of both devices to the exchange line is reliable prevented. Another advantageous development lies in this The underlying task is to reliably prevent double occupancy even in the case of reverse-polarity trunk lines. In addition, the faulty operating state of the polarity reversal should inform the user in a way which on the one hand still involves the use of one of the apparatuses allows, but on the other hand, the presence of a disturbance is also certain for the layperson recognizable.

The invention is based in particular on the knowledge that by a Increase the permissible stimulus resistance in a range of approx. 400 ohms simplified circuit is possible. With the task of reverse polarity protection - but Inclusion of additional features, which only limited you if the polarity is reversed Allow operation and thus notify the user of the disrupted operation in particular through the use of modern bistatic (bipolar) relays with two Windings and two changeover contacts are an exchange line-fed switching device feasible, since these only require approx. 90 to 100 mW excitation power. By increasing the stimulus resistance, it is possible to use one of the windings of the bistable Lay the relay directly in the connection line.

By increasing the incentive resistance to around 200 ohms If necessary, it would also have been possible to go to the intercom lines 1 and 2 to switch one winding each of relay A and B. This easy way waiving the setting circuit according to the main patent a telephone device to execute, but failed because with simultaneous occupancy of both microphone units len, Due to the division of the current, neither of the two relays may respond. This would lead to an undesired simultaneous loop current at low loop currents Activation of both microphone units come.

In order to avoid this situation, the line to SpSt 1 is again the set circuit (active three-pole) inserted. However, with one to about 400 Ohm increased stimulus resistance, so that the voltage drop when occupied at the same time between a- and b-wire the SpStl is sufficient to activate the relay via the set circuit A to switch. The set circuit in one branch of the circuit thus prevents the Parallel operation of two call stations.

The reset circuit is opposite to the circuit according to the main patent .... changed in that the bridge rectifier was replaced by a simple diode is, i.e. the reset circuit works depending on the polarity. In this way you can the advantage of identifying the undesired operating state of reverse polarity towards the exchange line, because the active three-pole circuit in the event of polarity reversal is not reset.

This ensures at the same time that there is no reverse polarity in addition, the occupancy of SpSt2 is interrupted by SpStl. Because that Relay A is switched independent of polarity, SpSt2 remains even after connecting SpStl switched off.

In another preferred variant, circuit means are provided, which, if the outside line is polarized, an ac- activation of the three-pole connection even with a current flow through those connected in the direct current path of the other Relay winding lying in the apparatus trigger, which switches on this apparatus caused by polarity correct connection.

Advantageous further developments of the invention are set out in the subclaims marked or are shown in the following illustration together with a preferred embodiment of the invention described in more detail. They show: FIG. 1 a block diagram of an exemplary embodiment of the circuit according to the invention and FIG. 2 a detailed Circuit diagram from which the implementation with discrete components and the control sequence in detail.

In the embodiment shown in FIG. 1, FIG 1 the basic connection of the two call stations to the main connection line reproduced.

The arrangement corresponds to the connection of call station 1 those according to the main patent, whereas with regard to the microphone station 2 instead of the Loop detection SE the "set" winding of the relay B is provided.

The loop detection and the resulting activation of the Setting circuit S is independent of polarity, while the polarized relay B only occurs when polarity correct connection to the trunk line HAS1 or the extension line NAS1 takes place.

The reset circuits are each a polarity-dependent reset the setting circuit S for the call station 1 is therefore only with correct polarity Operation possible.

From the circuit of Figure 2 is a detailed circuit of the individual assemblies can be seen, with the functions of the circuit of the individual Assemblies essentially correspond to those according to the main patent.

The description of the function of the circuit will now be given simultaneously Reference to the block diagram according to FIG. 1 and the circuit diagram according to FIG 2 take place.

When removing the first device (SpStl) it closes with the correct polarity Connection of the trunk line as well as polarity reversal charges the voltage drop at the resistor R3 via the resistor R6 on the capacitor C6, so that - depending on Polarity of transistor V2 or V3 turns on. The resistor-capacitor combination R6 / C6 is dimensioned in such a way that there is no response to alternating ringing voltage.

The output signal is rectified via diodes V10 to V13 the transistors V2 and V3 in the manner of a bridge circuit, so that the control the winding AI of the bistable relay A located in this circle is independent of polarity after switching through a thyristor V4 connected in series with the winding A1 is effected.

The thyristor is powered by the voltage drop via its gate electrode ignited at a resistor R2, the Charging a parallel winding Al in series with a resistor R4 connected capacitor C7 the generation of a ensures sufficient switching pulse to attract the relay. One to the capacitor C7 resistor R5 connected in parallel prevents the capacitor from charging C7 by interference pulses or the like.

The winding AI of the relay A switches the input resistance via the contact al R3 briefly and thus connects the a-wire of the exchange line directly with the corresponding one Connection of the first device SpStl. The second apparatus will be at the same time severed. With this, the exchange line is switched on after the resistor R3 the winding of the relay AI of the relay to the apparatus SpStl in series for this purpose A lay parallel, now the internal resistance of the apparatus 1 directly as a mediation incentive presented, whereby the respective total resistance depends on the standard-compliant connection resistance of an apparatus deviates at most slightly.

With the contact a2 of the relay A with activation of the relay A the winding AII together with the reset circuit, which with respect to the component arrangement essentially corresponds to the setting circuit with respect to the winding AI, prepare to the terminal W1 of the apparatus assigned to a corresponding hook switch contact 1 connected. The reset circuit works as a result of being connected in series Diode V14 depends on the direction of the current, i.e. only when connected to the exchange line with correct polarity HAS1 connected telephone equipment.

This dimensioning ensures that for apparatus 1, too an external line seizure takes place when the resistance of the external line is increased, if the increase is to be observed in the operation of simple telephone sets Limits.

If device 2 (Spst 2) is lifted - with device 1 on-hook, so the relay B speaks about its in the line A, which with the corresponding Connection of the apparatus 2 is connected to the winding BI of the relay B on. The relay responds depending on the polarity, with the winding BI for Alternating ringing voltage through the series connection of the resistor R1 with the capacitors C8 and C9 are bridged. The contacts bl and b2 of the relay B are corresponding the contacts a1 and a2 - related to the other connected device -arranged. The relay B does not respond to the reverse polarity of the trunk line, so that this state is signaled to the subscriber as a malfunction at the latest, if by removing the first apparatus during one over the second apparatus The second set is switched off during the call.

Since the relay B was not activated and thus also not the contact bl reached its second position, relay A responds via the Winding al still possible without further ado.) Because the reset circuit for the relay A also works depending on polarity, the relay A remains in the through its Winding AI generated layer and the apparatus 2 permanently switched off. An external call is no longer possible on this telephone, so that the corresponding state causes the subscriber to inform the fault location.

Such an obviously disturbed operation also exists if if due to a large line resistance the flowing through the winding BI There is not enough current to activate relay B, so there is no safe shutdown of apparatus A takes place. Since this one with a more sensitive activation circuit is equipped, it will take off even if the line resistance conditions have deteriorated by response of the relay A to the second apparatus "the line away", so that too In this mode, a simultaneous connection of two devices to the exchange line is certainly prevented.

In a preferred development of the invention, the reset winding AII of the relay A dimensioned in such a way that a reset of the relay A to a degree increased line resistance, so that a response of the relay B via its winding BI is prevented, is excluded. In this case - as with polarity reversed Connection - also only if there is an unexpected increase in the resistance of the exchange line still be possible to use the first device, so that also in this respect a there is additional information about the existing malfunction.

A polarity-dependent connection not shown in the drawing (Diode or the like) from the connection A2 of the second apparatus facing winding end of the winding BI to the bases of the transistors V2 or V3 would be if the second set was removed and the polarity of the exchange line was reversed j with the corresponding polarity of the diode) a response of the relay A with the with it cause associated shutdown of the second apparatus, so that also a immediate detection of the malfunction would be possible when removing the second device (Transistor V3). To address the winding AI would be a diode in the forward direction from the cathode of the thyristor V4 to the terminal B2 of the second apparatus.

The circuit shown is the activation circuit of the relay A much more sensitive than that for the relay B, so that at the same time When both devices are lifted, device 1 is given clear priority, and so too a parallel connection of both devices to the exchange line is reliably prevented is.

The reset circuit with the winding BII for the relay B corresponds essentially that for relay A, with the aid of a diode V15 as well a polarity-dependent reset only if the exchange line is connected with the correct polarity is effected.

The invention is not limited in its implementation to the above given example. Rather, a large number of variants are conceivable, which of the solution shown is also used in the case of fundamentally different designs do.

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Claims (4)

Circuit for recognizing a loop state Patent claims 1. Circuit for detecting a loop state in a telephone device below This status is signaled by forwarding the closure of the loop to a Telephone line from which the circuit is supplied with power, in particular to trigger functions within the telephone equipment, with an active three-pole connection between the connected telephone and a first line wire is switched on and when current flows through this circuit as a result of the closure of the loop its resistance between the connection point at the first Line core and a further circuit point reduced, the further circuit point is connected to one terminal of a winding of a bistable relay, the other Connection to the second line wire is connected, the bistable relay at such a winding current caused by the reduced resistance in the three-pole moves from a first to a second stable position, and a reset circuit, which can be activated in the second stable position of the bistable relay, d a d u r c h g e k e n n n z e i c h n e t that with a telephone device with at least one other connected device (Sp St 2) only one of the devices an active three-pole (SE) is assigned while in the direct current circuit of the other connected apparatus a winding (B I) from one assigned to this apparatus Relay (B) is provided and the response speed or sensitivity of the active three-pole is selected to be greater than that of the relay (B). 2. A circuit according to claim 1, d a d u r c h g e -k e n n z e i c h n e t that the active three-pole (SE) responds regardless of the direction of the current. 3. Circuit according to one of the preceding claims, d a d u r c h it is noted that the reset circuit (RSA) for the active one Three-pole assigned relay (A) responds depending on polarity in such a way that a reset process only if the telephone system is connected to the exchange line with the correct polarity he follows. 4. Circuit according to one of the preceding claims, d a d u r c h g e k e n n n n e i c h n e t that circuit means are provided, which in the case of reverse polarity Trunk line activation of the three-pole circuit even when current flows through the relay winding in the direct current path of the other connected device trigger which a switch-on of this device with correct polarity connection causes.