DE2622732A1 - Subscriber telephone with dialling pulse generator - has contacts shorting keyboard and pulse generator in rest state and during calls - Google Patents

Abstract

The dialling pulse generator is short-circuited in the telephone instrument rest state and during calls, and is operated by a keyboard. When a key is operated when the loop is closed, the short-circuit passing through switching contacts and a bistable switch, is removed and the required number of pulses delivered by opening pulsing contacts between the two line wires. The pulsing contact is in series with a contact, closed only when a key is operated. A switching device monitors the potential between the two contacts and trips a bistable switch into its position shorting the keyboard and the dialling pulse generator when a contact is closed without simultaneous closure of the other contact.

Description

Circuit arrangement for subscriber stations in

Telecommunication, in particular telephone systems with a keypad controllable dial pulse generator The invention relates to a circuit arrangement for subscriber stations in telecommunication systems, in particular telecommunication systems with a short-circuited in the idle and call state and through a keypad in the Way controllable dial pulse generator that with a closed line loop key actuation taking place while canceling the over with each key actuation switching contacts and a bistable switching element running short-circuit in each case a number of dialing pulses assigned to the pressed key by clockwise Opening of a pulse contact switched between two wires of the connecting cable is delivered. The short-circuiting of the dial pulse generator with the dial pad is used in addition, no additional call attenuation by this during the call state To evoke facilities.

Now it can happen that especially when the bistable Switching element consists of a bistable relay, this by impact or shock is brought into its respective working position and thereby in an unintentional manner prevents a conversation because when the short circuit is canceled the bridging the two wires of the connecting cable.

Also a bistable electronic switchover element could be overturned by glitches in the respective working state and thereby make conducting a conversation impossible or at least severely prevent it. These however, disruptive switching of the bistable switching element into the working position can not only during a conversation, but also in the resting position and even if in this state the reception of the call signal at the station concerned is not hindered, the subsequent conduct of the conversation is impossible made.

The object of the present invention is therefore to do this to ensure that the switching element forcibly due to the respective call status is transferred to its starting position if a dial button is not pressed at the same time became. This resetting of the bistable switching element must be done very quickly, so when a station is called, just pick up the receiver to answer it of the call an existing short circuit is separated so that the called party is in no way hindered in conducting the conversation.

The invention achieves this in that the pulse contact with a only when a key on the keypad is pressed, the contact is closed in series and that the potential between the two contacts monitoring switching means at Closure of one contact switches the bistable switchover element into which cause the keypad and the dial pulse generator to short-circuit. This can be done in a simple manner that the only when a button is pressed, the contact closes the series connection of a Zener diode is connected in parallel with a capacitor, the charge or discharge current of which the Switching of the bistable switching element into the respective starting position causes.

An exemplary embodiment of the invention is shown in the drawing. 1 shows the circuit diagram of a telephone subscriber station with the connection points the touch dial device reproduced in FIG. 2 and the circuit arrangement in FIG. 2 a dialing device with a dial pad and a dial pulse generator.

As shown in FIG. 1, the touch dial device shown in FIG TWB with the connection points 1 and 2 in one wire of the connection line and with the other connection point 3 connected to the other wire of the connection line. Will the connection point 1 is connected to the connection point 3, which is via the push button selection the pulse contact occurs, the rest of the station circuit is disconnected and affected so that the signaling is not. In the idle state, the touch dial device TWB is short-circuited, which is also the case in the conversation state, so that incoming or outgoing guided Calls by the touch dial facility TWB are not additionally attenuated.

As Fig. 2 shows, are in the idle state and in the call state Connection points 1 and 2 on the rest side of a common key contact GT2 and the rest side of the changeover contact a connected to one another. The changeover contact a is actuated by the bistable relay A, which is switched over by the charging current of the capacitor G3 and its switching back either by the discharge current of the Capacitor C2 or the discharge current of the capacitor C3 takes place. The power supply is taken from the speech loop in the manner still to be described, so that none special voltage source is to be provided. The impulse is given by an electronic one Impulse contact formed by transistors T1, T2 and T3.

There is also a so-called "reverse polarity protection" built in to the Ensure the function of the touch dial device even if the two wires are interchanged. Diodes D1, D2, D3 and D4 serve to protect against polarity reversal. The transformation of the entered via the coding contacts f2, f3 'f4, f6 and f7 of the keyboard WT Choice information happens in the respective pulse train corresponding to the pressed key in a numeric generator module ZGB, which can be influenced by a clock generator module TB is. The latter module also provides a signal the first time a button is pressed in order to reset the memory of the ZGB numerator module to its original position. For an understanding of the present invention, the structure and the mode of operation are of the numeric generator module ZGB and the clock generator module UB are not necessary, see above that a corresponding description and explanation can be dispensed with.

With the pulse contact formed by transistors T1, T2 and T3 there is another contact in series, which is formed by transistors T6 and T7 will. The connection between that formed by transistors T1, T2 and T3 Impulse contact is with the contact formed by transistors T6 and T7 to a voltage monitoring device, consisting of the Zener diode D19, via a capacitor C2 is charged after the breakdown voltage has been reached. Its charging or discharging current is used to reset the bistable relay A in its rest position, if such a reset is necessary during a call will.

Pressing a key on the WT keypad is used by each Button actuated contact GT2 the short circuit of the connection points 1 and 2 in Fig. 2 repealed. The current flowing through the telephone loop now flows through the Diodes D1 or D3 of the reverse polarity protection and the electronic pulse contact T1 and T2 as well as the transistors T6 and T7, the Zener diode D16, the diodes D14 and 1) 15 and finally via one of the reverse polarity protection diodes D2 and D4 to the supply device return.

The voltage supply for the circuit arrangement shown in FIG is taken in parallel with diodes D14, D15 and D16. The level of the supply voltage is primarily determined by the Zener voltage of the Zener diode D16. Demanded there is, the voltage drop between connection points 1 and 2 is smaller during the selection or at most equal to 5.5 volts will be held during the free time that already expires before the first pulse, the capacitor C1 to a higher voltage, for example 8 volts charged. This capacitor takes over then during the time of a series of impulses, i.e. for a maximum of one second the energy supply of the circuit arrangement shown in FIG. During the recharging of this capacitor is not possible because of individual pulse pauses during this time the supply device consisting of diodes D14, D15 and D16 by the transistors T9 and T10 and the diode D25 is bridged to between the connection points 1 and 2 the voltage drop in the specified limit, so to hold up to a maximum of 5.5 volts. The voltage drop would also occur during the free election period be held between the connection points 1 and 2 at this level, so could the capacitor C1, due to the flow voltage of the diodes D1 to D4 of the reverse polarity protection and the saturation voltages of the transistors T2, T3, T6 and T7 only to one much smaller value, for example 2 volts. This amount but would be far too low for the supply voltage of the ZGB numeric encoder module.

The capacitor Ci is charged via a current limiter circuit, consisting of the Zener diode D16, the resistor R23 and the transistor T8, the when the breakdown voltage is reached, the diode D16 becomes conductive and thus the Charging of the capacitor C1 allows. The emitter-collector path of this transistor the diode D17 is connected in parallel.

If one of the keys on the WT keypad is pressed, the other common key contact GT1 ground potential on the common information input Com of the numerator module ZGB given, while the other information inputs C1, C2, C3 and C4 depending on the key pressed via the coding Contacts f2, f3, f4, f6 and f7 can be connected to E £ dpotential. As the transistors i'2, T3, T6 and T7 are switched through, takes place via the transistor T6 and the Diode D13 charges the capacitor 04.

As a result of this charging, the transistor T16 switches through and gives a negative pulse to the input Dat of the clock generator block TB. At the exit Q of this block then appears for a short time earth potential, which is above the Input Re of the numeric transmitter module ZGB the memory elements of this module in bring their respective starting position. The capacitor C4 prevents during pulsing while which the transistors T2 and T3 are not conductive, a renewed activation of the transistor X16 and thus a deletion of the memory in the ZGB numeric transmitter module during delivery election information. Only approx. 400 ms after the last key was pressed or when hanging the receiver, i.e. when resetting the hook switch contacts GU1 and GU2 in Fig. 1 during a dialing handover, the memories are replaced by a new one Pressing the button brought back to the starting position.

The ZGB numerator module is required to create the series of voting impulses two time-shifted clocks sent by the clock generator block TB via the outputs 1 and 3 can be delivered.

The via the common key contact GT1 and the coding contacts f2, f3, f4, f6 and f7 of the keyboard WT to the information inputs Com, C1, C2, C3 and C4 of the numerator module ZGB created dialing information is from this on The end of each reset signal applied to the input re is recorded and saved. after the dialing information has been written into the numeric transmitter module ZGB appears at output M of this module ground potential and remains in this state until the end of the last dialing pulse delivered an election information stored in the ZGB pager module.

The number transmitter module can store a large number of digits and send them out one after the other in the form of a series of pulses.

When the supply voltage appears, i.e. after disconnection the short circuit between the connection points 1 and 2 in Fig. 2 by opening of contact GT2 the capacitor C3 is charged via the conductive transistor T14, while the transistor T15 later, i.e. with the appearance of the at output M of the encoder module ZGB occurring signal becomes conductive. The transistor T15 blocks through its collector potential the transistor T14 and a discharge of the capacitor now takes place via the diode D23 C3 and thus a tilting of the relay A in its working position. There now the contact a toggles, can when releasing the button, so when resetting the common Key contacts GT1 and GT2 no new short circuit between the connection points 1 and 2 are produced. Rather, the switched contact a bridges over the resistor R8 the speech circuit of the telephone set, so that the dialing noises can be heard strongly attenuated.

At the end of the last dialing pulse, one disappears into the encoder module ZGB stored dialing information is present at the output M of this module Signal, the transistor T15 returns to its non-conductive state and the transistor T14 switches through again and enables charging of the capacitor C3 The part of this charge on the excitation winding of the relay A positive pulse reaching relay A tilts back to its rest position. So that the connection points 1 and 2 are short-circuited again, via the Quiet since the common key contact GT2 as well as the quiescent side of the contact a. There is a normal voice connection, which is established by the circuit arrangement Fig. 2 is not additionally attenuated.

However, it is now possible that the relay A, be it overturned by a bump or blow or for any other reason and thus the connection points 1 and 2 are no longer bridged. This can upset can also be done in the idle state and is noticeable when a participant is due of an incoming call unhooks its receiver. In this case it would be his Speech circuit is strongly attenuated by the circuit arrangement according to FIG. 2, if the arrangement according to the invention would not be provided. This causes a through-connection does not come about via the transistors T1, 'D2, T3, T6 and T7, if not at the same time one of the dialing buttons is pressed, since it is only pressed when the line loop is closed causes the switching on of the transistors T6 and T7. The connection of this Transistors T6 and T7 depends on the through-connection of the transistor T4, its Basis is only supplied with the corresponding control potential if the common Key contact GT1 ground potential via the diode D11, the resistor R20 and the diode D8 feeds.

Due to the lack of control of the transistor T4, the voltage at the Zener diode D 19 rise so far that it breaks through. It is now over the transistors T2 and T3 as well as the diodes D18 and D19 of the capacitor C2 charged. If the charging voltage of this capacitor C2 reaches a certain value, the Zener diode D21 breaks down and ground potential is established via the transistors T11 and T12 connected to the excitation winding of relay A, which returns to its rest position after approx. 0.2 ms tilts. As a result, the capacitor C2 can no longer be recharged and it discharges via the transistors T11 and T12 and the relay A. Since the resetting of a about switched bistable relay in its initial position very quickly, so takes place in a time span of approx. 2 ms due to the circuit arrangement shown, this switchover is neither for the called nor for the when the handset is lifted call ends subscriber noticeable.

The output L of the numeric transmitter module ZGB blocks during the impulse transmission via the transistors T1 and T5, the transistors T2 and T3, so that the loop is interrupted. The transistors thus form the pulse contact, with the number of these blocks in the context of a series of pulses of the number of pulses to be transmitted is equivalent to. Via the output Str of the ZGB number generator block, every Impulse generation a through-connection of the transistors T9 and T10 and thus the one described above Shutdown of the power supply device during the impulse series, so that the officially prescribed insertion loss is observed during this time can be. -

Claims (3)

Claims: Circuit arrangement for subscriber stations in telecommunications, in particular telephone systems with a short-circuited in the idle and conversation state and by a keypad in such a way controllable dial pulse generator that at a when the line loop is closed, key actuation with cancellation of the contacts that switch over each time a key is pressed, as well as a bistable switching element running short circuit in each case a number assigned to the pressed key of dialing pulses by intermittently opening one between two wires of the connection line switched pulse contact is output, characterized. that the pulse contact (T2, T3) with a closed only when a key on the keypad (WT) is pressed Contact ('p6, T7) is in series and that the potential between the two contacts Monitoring switching means (D19, part, T12) when one contact closes (T2, T3) without simultaneous closing of the other contact (T6, T7) the switchover of the bistable switching element (A) into the keypad and the dial pulse generator (TWB) cause short-circuiting position. 2. Circuit arrangement according to claim 1, characterized in that the contact (T6, which is only closed when a key on the keypad (WT) is pressed) T7) the series connection of a Zener diode (D19) with a capacitor (C2) in parallel is switched, the charging or discharging current of the switching of the bistable switching element (A) causes. 3. Circuit arrangement according to Claims 1 and 2, characterized in that that the charging voltage of the capacitor (C2) through another Zener diode vD ° 1j The bistable changeover relay is monitored and when the Zener voltage is reached (A) is switched into the discharge circuit of the capacitor (C2).