DE3245839A1 - Circuit arrangement for identifying a loop state - Google Patents

Abstract

Circuit arrangement for identifying a loop state in a telephone device and for signalling this state through transfer of the loop closure to a telephone line from which the circuit power supply is provided, with an active triple pole which is inserted between the connected telephone set and a first line wire and which reduces its resistance between the connection point on the first line wire and a further connection point when current flows through this circuit due to loop closure, where the further connection point is linked to one connection of a winding of a polarised relay, the other connection of which leads to the second line wire, the bistable relay switches from a first into a second stable position in the case of a winding current of this type produced by the reduced resistance in the triple pole, and a reset circuit which is activated in the aforementioned position of the bistable relay.

Description

description

The invention relates to a circuit as described in the preamble of the claim 1 specified Art.

In telephony technology there is often the problem of a circuit indicate which is capable in a connected telephone set or a device to be connected to a telephone line to be recognized as a sign of its activation.

This information should now be used in multiple ways - depending on where applicable of further conditions, which are determined by the application - as loop formation passed on to a trunk or extension line in order to provide a transfer incentive to create. The fact often plays a role in the design of such a circuit a role that very little space or no additional power supply is available stand.

The object of the invention is to provide a simple circuit here indicate the - in particular in the form of their further training - that are involved in the application meets the requirements to be placed in a telephone network.

A preferred embodiment relates to a so-called "A2 circuit". In telecommunications technology, the term "A2 connection" means the possibility of connection of two telephones on a main or branch line (HAsl, NAsl). There a simple parallel connection of the devices is not permitted for this Scarf- previously special devices with extended hook switch needed. Such an apparatus is used as the first apparatus and switches the downstream second device when it is occupied. A normal telephone set can be used. The disadvantage of this circuit is there in that the first set always has priority, i.e. if from the second set an assignment has already taken place, it is confirmed by removing the handset interrupted by the first set.

However, the application of the invention is not limited to one such an A2 circuit is limited, but is also suitable for parallel connection suitable for a larger number of devices or corresponding accessories.

The requirements to be placed on an A2 circuit in particular are For example: No exclusive priority for one of the two participants.

Possibility to install the circuit including the necessary clamping and plug connector in a flush-mounted junction box.

Possibility of using simple devices without an extended hook switch.

No special mains supply, i.e. power supply for the circuit from the official website.

The function of the circuit should be independent of the polarity of the Connecting cable.

The task is solved with the in the characterizing part of the Claim 1 specified measures.

From the solution found result, possibly with inclusion of further training, in particular the following advantages: The circuit can be because of the small number of relays required, which are also available in a small design in a small flush-mounted box with a diameter of 55 mm.

The additional DC resistance of a corresponding A2 circuit can be less than 100 ohms in the stimulus state (occupation) and less in the conversation state than 40 ohms.

The advantage of the so-called selector star switch capability is given, there e.g. no rectifier bridge circuit with semiconductor diodes, as they are otherwise would be necessary for polarity independence, which is unfavorable for small currents Resistance behavior must be switched into the line.

An additional attenuation of less than 0.2 dB during a call is complied with, which means that one switching means in the line is less than 30 ohms should be real. One between a- and b-core lying Resistance should have a value of more than 15 kOhm.

There is a conversation between the two sets of the circuit a crosstalk attenuation of more than. 75 dB complied with.

The function of the circuit can be determined in a supply current range of 17 ... 60 mA.

The additional DC resistance in the line during the Call state is a maximum of 40 ohms.

The device that is not in use is switched off in two poles.

Operation on normal exchange lines as well as branch lines.

That is necessary for the separation of the unoccupied microphone units Relay does not drop out during the dialing process, whereby the holding circuit is more than 15 kOhm can be. (A corresponding monostable relay would have to be active during the dialing process hold in the event of loop interruptions of less than 80 ms and when triggered drop after a period of more than 100 ms, which is a corresponding dimensioning would also require the resistive components of the necessary time constants.) Advantageous Developments of the invention are or will be characterized in the subclaims at the next The following illustration of a preferred embodiment the elf in dung described in more detail. The figures show: FIG. 1 a setting circuit according to FIG Invention, which is suitable as an assembly, the necessary for loop formation Perform switching operations, Figure 2 a reset circuit as a supplement to the set circuit according to Figure 1, Figures 3 to 5 embodiments of A2 circuits, which under Use of the circuit assemblies according to Figures 1 and 2 are constructed and Figure 6 the circuit according to the exemplary embodiment according to FIG. 3 with dimensioning.

The circuit represents a possible solution with a small footprint according to Figure 1.

Assuming that there is negative on the a-wire and the negative on the b-wire Main or branch line (HAsl resp.

NAsl) positive potential is created when the loop closes through the connected telephone FeAp a voltage drop corresponding to the polarity across a resistor R1 which is connected in series with the telephone set.

The opposite of the emitters of two transistors T1 and T2 positive The voltage drop passes through a coupling resistor R2 while charging a capacitor C1 to the base of transistors T1 and T2. This will make the npn transistor T1 conductive, while the pnp transistor T2 remains blocked. Via the transistor T1, and a capacitor C2 is charged via diodes D2 and D3 of a rectifier bridge. A resistor R3 has only a protective function in the circuit and can, depending the maximum permissible collector current of the transistors used, if necessary omitted.

If the polarity of the connection cable is reversed (a- and b-wire interchanged) becomes a negative potential when occupied by the voltage drop across resistor R1 transmitted to the base of the pnp transistor T2. A transistor T2 switches over the Diode D1 positive potential to one pole of the capacitor C2, while on the Diode D4 the negative potential of the b-wire reaches the other pole of the capacitor.

After exceeding a predetermined voltage on capacitor C2 is switched via a suitable non-linear switching means NE by means of a switch S. a bistable relay A via its corresponding winding from a first stable one Switch position transferred to the second and closes the entire loop detection briefly about your own contact. This results in an insertion loss of less than 0.2 dB reached. The non-linear switching means is preferably a thyristor, whose gate electrode is activated by means of a voltage divider, or by a corresponding switching means realized. (see also the corresponding circuit parts in the reset circuit according to FIG. 2 and the illustration according to FIG. 6).

The diodes D1 and D2 fulfill a protective function for the transistors T1 and T2. They each prevent reverse polarity of the collectors of the transistors and thus an inverse operation.

The capacitor C1 prevents together with the common base resistance R2 the switching on of the transistors during a pending alternating ringing voltage. By omitting or temporarily disconnecting this capacitor, the circuit is complete suitable for recognizing dialing characters issued by the connected FeAp telephone set, whereby the recorded via a corresponding contact of the bipolar relay Pulses to corresponding circuit parts of the switching part of a private branch exchange let pass. The circuit according to the invention is thus able in a PABX also has the function of dialing recognition due to slightly different wiring to take over.

The resistor Rl connected into the line is dimensioned so that with a minimum loop current there is a voltage drop of (approx.) 0.6 V to the Control of the translators drops. This results in a for resistor R1 Value greater than 35 ohms. The "loop" created by the lifted device is therefore switched through to the connection line and calls an exchange line accordingly emerged.

A varistor V is used to protect the transistors in the event of overvoltages on the line. The breakdown voltage of the varistor is selected to be lower than the reverse voltage of the transistors used.

After termination of the occupancy by the telephone set is the Cancel the exchange loop when the hang-up is detected. It has to be an apparatus -assigned bistable relay, which is addressed via its pick-up winding after assignment has, through a suitable circuit when hanging up the handset on its second Winding into its resting state.

A connection of the second winding could appear suitable for this as voltage monitoring between tip and ring.

Due to the internal resistance of the telephone set of approx.

300 ohms results in a voltage depending on the loop current of 5.1 ... 14 V on the wires. When you hang up, the full supply voltage is established for example 60 V, and that would be a criterion for the "on-hook" state given. The disadvantages of such a circuit would be that loop interruptions of less than 80 ms during the dialing is not yet used as a criterion for hanging up would be evaluated, i.e. in addition to the voltage monitoring, a temporal over monitoring take place. This circuit would always be parallel to the during the call Apparatus and would cause undesirable additional attenuation.

A much better solution for recognizing the hanging up is shown in FIG 2 reproduced. Their function is based on the use of one in newer telephones hook-and-loop switch available in every version, the rest of the connection serves as a second alarm clock. When the handset is on-hook, connection W is via a Hook switch contact GU 1 is connected to the a connection and is disconnected when it is occupied.

FIG. 2 shows a reset circuit using the W connection. After activation of the bistable relay via its winding by the loop detection and reset circuit, this relay becomes a reset circuit via its own contact switched between W and b connections in preparation (as can be seen from the following to Descriptive Figures 3 to 6 can be seen).

When hanging up, a rectifier bridge is switched on G and a resistor R4 a charging capacitor C3 up to a predetermined voltage loaded.

After exceeding the corresponding voltage, a Zener diode Z in series with a resistor, forming a non-linear voltage divider R5 ignites a thyristor Th in parallel with a capacitor C4 and discharges one Capacitor across the reset winding AII of the bistable relay. The relay switches at the same time with a corresponding own contact from the W or b connection so that the reset circuit is not in the ringing circuit when there is an incoming call lies.

The block diagrams according to FIGS. 3 to 5 show possible solutions an A2 circuit, which can be accommodated in a junction box.

Common to all circuits is the loop detection with a setting circuit, as well as the reset circuit using the W connection.

Furthermore, it is prevented in all circuits that - for example due to vibrations - the bistable relays in a wrong position switch and hold the circuit in an undesired switching state can. The cut-off contacts for the individual windings ensure that the circuit out of a faulty circuit at any point in time into the correct one State passes.

All the proposed circuits work together particularly favorably with connected devices, which contain transistor speech capsules, because with it a defined internal resistance of the device is guaranteed.

This should not be seen as a limitation, as future telephones will anyway no more charcoal speaking capsules will have.

In the embodiment of a circuit of Figure 3, the two are Circuit parts assigned to each apparatus are constructed completely identically. Thus, no apparatus is privileged in any form. Flows in the circuit when occupied e.g. from the SpSTl intercom the contact b3, the loop detection 1, the apparatus circuit SpSTl and the contact b4 to the b-core. The relay A responds and switches with its contacts a3 and a4 from the SpSt2 intercom.

At the same time, the loop detection 1 is short-circuited via the contact al and the reset circuit is switched on in preparation via contact a2. When hanging up the reset circuit A is activated via the idle side of the GU 1 and disconnects via the contact a2 then off again itself.

In the circuit according to FIG. 4, loop detection is carried out via the Quiescent side of the hook switch contact GU I of the first apparatus led. So that will if both microphone units SpStl are occupied at the same time, the second one immediately Intercom station SpSt2 disconnected. The voltage drop thus falls for the setting circuit S1 only one device (approx. 300 ohms). This means that the set winding can have a correspondingly higher resistance and the capacitance of the capacitor C2 can be made correspondingly smaller.

Due to the single-pole disconnection of the a-wire when the first one is occupied Call station SpStl, the alarm capacitor of the second call station can also be used SpSt2 is not discharged, which means that SpSt2 also occurs at the second intercom station when occupied and hung up, not to the alarm clock.

In this circuit, for example, flows from the call station when it is occupied SpStl loop current from the a-wire, the contact bl, the apparatus circuit, the Loop detection 1 and contact b3 to the b-wire. Via your own hook switch GU I, the a-wire of the second apparatus SpSt2 is disconnected immediately, while after When relay A picks up, the b wire is also switched off via contact a4. The contact a3 short-circuits loop detection 1 and contact al switches again in preparation the reset circuit R1 on. The contact a2 prevents the Reset circuit R1 and the closed contact al the a-wire of the call station SpSt2 remains switched on.

When hanging up, the reset circuit R1 is again activated via GU 1, and the circuit goes to sleep.

In the circuit according to FIG. 5, it occurs independently of the polarity the line at no intercom to the so-called flckerpjngll, since both loop detections 1 and 2 are each disconnected via the hook switch contact GU I of the remote station will. A slight disadvantage of this circuit could be that that there is no speech loop when both microphone units are occupied at the same time comes. If the call station SpStl is occupied, for example, loop current flows via the a-wire, the contact bl, the. Apparatus circuit, contact b4, loop detection S1, the hook switch GU I, the call station SpSt2, the contact a2 to the b-wire. By actuating the hook switch contact GU I of the SpStl intercom station the b-connection of the second apparatus was immediately disconnected. After relay A has picked up the b-wire is connected directly to the b-connection of the device via contact al and bypassed the loop detection S1. The SpSt2 intercom is via the contacts a2 and a4 switched off on two poles. Contact a3 prepares the reset circuit R1 on, so that when you hang up the circuit is brought back to the rest position.

A practical embodiment of the circuit according to FIG. 4 with all the details and the dimensions of the components are shown in FIG. 6.

The connection of secondary alarm clocks is shown in the respective block diagrams specified. In the circuits according to Figures 2 and 3, the connection of secondary alarm clocks only possible at the correspondingly marked intercom station, otherwise the crosstalk attenuation worsens becomes and the value of more than 75 dB cannot be maintained.

All circuits are also suitable for operation on private branch exchanges suitable.

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Claims (11)

Circuit arrangement for recognizing a loop state P a t e n t a n s p r ü c h e 1. Formwork for recognizing a loop state in a telephone device and to signal this condition by forwarding the loop closure a telephone line from which the circuit is supplied with power, G e k e n n n z e i c h n e t through an active three-pole (1, 2), which is connected between the connected Telephone set (FeAp) and a first line vein is switched on and at Current flow through this circuit as a result of the loop closure between its resistance the connection point on the first line core and a further circuit point reduced, the further circuit point with a connection of a winding (AI) of a polarized relay is connected, the other terminal of which is connected to the second Line wire is connected, the bistable relay with such a through the reduced resistance in the three-pole winding current of one first reaches a second stable position, and a reset circuit (R1, R2), which is activated in the second stable position of the bistable relay. 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 in the second stable position of the bistable relay a contact (al in Fig. 3), which includes the three-pole (1) with respect to its not with the relay winding connected connections bridged. 3. Circuit according to one of the preceding claims, d a d u r c h it is not indicated that the active three-pole (1, 2) off two complementary transistors (T1, T2) controlled in parallel, at whose Collectors switched on a winding of the bistable relay via rectifier is. 4. Circuit according to one of the preceding claims, d a d u r c h it is noted that the reset circuit (R1, R2) responds to a voltage rise between the line cores, which is caused by the termination of the loop state in the connected telephone set is triggered, a current through a winding (AII) of the relay triggers, which return it to its first stable state leaves. 5. Circuit according to one of the preceding claims, d a d u r c h notices that for the connection of several telephones (SpStl and SpSt2) to a line pair several essentially similar circuits are provided, the relays of which have at least one additional contact (a3, b3 in FIG 3), which in the second stable state of the relay causes the relay to respond prevents further switching. 6. Circuit according to one of the preceding claims, d a d u r c h it is not indicated that the reset circuit has a second winding (All, BII) of the bipolar relay controls. 7. A circuit according to claim 6, d a d u r c h g e -k e n n z e i c h n e t that the reset circuit between a line wire and the connection (W) for the idle side of the fork changeover contact connected to the other line wire (GUI) of the connected telephone set is switched on. 8. Circuit according to one of the preceding claims, d a d u r c h it is noted that the set and / or reset circuit for control a winding of the bipolar relay has a non-linear circuit (Th) which in response to an ignition pulse, their resistance in series with the winding is greatly reduced. 9. Circuit according to one of the preceding claims, d a d u r c h it is not indicated that the winding (AI, BI) of the bistable relay, the belongs to the setting circuit, through a capacitor (C2) for the ringing alternating current is bridged. 10. The circuit of claim 9, d a d u r c h g e -k e n n z e i c h n e t that the bridging of the winding by the capacitor (C2) at least is canceled for the time of the dialing recognition, whereby von'einem of the connection points the pulse dialing signal for controlling a connected private branch exchange is derived will. 11. Circuit according to one of the preceding claims, d a d u r c h e k e n n n e i c h n e t that the circuit (1, 2 in Figures 4 and 5) for the loop detection between a line core connected via a first one Telephone set to the connection for the quiescent side of the with the other line wire connected hook switch of another connected telephone set is turned on.