DE2228205B2 - Ringer decoder - Google Patents

Description

The invention relates to a ringing tone decoder based on responds to first and second ringing tones of different frequencies received in sequence with a first circuit for receiving and selecting the first tone, a second Circuit for receiving and selecting the second tone, an integration stage with resistor and Capacitor and a blocking circuit to the off sending a warning tone without previously receiving it to prevent the first call tone.

For various high-frequency paging systems, low-frequency ringing tones are used to respond to the selectively operating decoder to a specific one Switch on the receiver or trigger display or warning tones for certain receivers. Although at In a simple system a single ringing tone is sufficient for the selection, it is useful to have several ringing tones to be used for a larger number of selekti ven calls used in various combinations will. A relatively simple and reliable system can be created with two low-frequency ringing tones that are issued in succession. Such a system works

However, rides incorrectly when two for engagement pjaes decoder required tones on the transmission line as a result of music and speech transmission or interference noises occur due to their Frequency position you can switch on the decoder a To switch this option off, the ring tones for a certain period of time ur.-J by a certain tone-free periods of time, so that the decoder tones with a different tone Can exclude clock ratio. A solcb € S Rufsystens is already through the US FS 34 6 294 known to, however, selective call systems and in particular DeV / Kler also in very small electronic Devices such as B. in portable HF and call receivers », To be able to accommodate, it is necessary that the decoder on the one hand takes up very little space and on the other hand has a minimal need for electrical power for excitation Decoders can be met with an integrated circuit structure; however, to take advantage of the low Manufacturing costs due to mass production for the integrated circuit can be exploited a it is necessary that the ringer decoder circuit is in such a way is constructed so that it is not only in the one in the following Description mentioned radio telephone, Sondem can be used with any type of remote control that works with such different tones which are sent out from a control station will. The connection between the transmitter and receiver can be via a wire or via radio take place.

From the DT-AS 11 79 272 there is already a circuit arrangement for the selective evaluation of a specific signal which is characterized by its frequency Alternating currents with the help of one half-wave determining the length of the incoming half-wave and one that follows it Way determined signal associated output activating timing device, in particular for the Tone frequency selection in telephone systems, known, whereby when receiving the individual alternating current half wave at an output of the timing device occurring voltage pulses to one of the relevant Output associated storage capacitor are supplied and when a certain state of charge is reached this storage capacitor will take effect, switching means the output of one of the recorded S. <jnal initiate the characteristic output criterion 11s. The charging voltage of the capacitor is monitored by a Zener diode when it is reached their breakdown voltage causes a trigger circuit to emit an output pulse will. By emitting the output pulse, a switching device is activated that influences the discharge of the storage capacitor brings about.

The present invention is based on the object one that can be produced as an integrated circuit and has a low-power, low-voltage battery and a relatively large spa-ming fluctuation range working call tone decoder to indicate the two successively occurring, frequency-different Ringing tones, which are in a certain pulse and time relationship to each other, responds, but without being caused to malfunction by interference signals of the same frequency, and that by adding a further circuit to one responsive to a single tone that is present for a relatively long time Group call decoder can be expanded, which can be recognized by the type of warning tone whether it is a selective call or a Group call

This task is achieved in that the capacitor of the integration circuit, which is initially charged to full voltage, is discharged through the switch that responds to the first tone (A) during the duration of the first tone (A) and after the first tone (A ) recharges, that a first Triggersc.halterung, which is arranged in the first circuit is coupled to the capacitor, that the trigger circuit generates a first voltage pulse as soon as the voltage of the integration capacitor has risen to a certain value after the first tone (A) has decayed is that a second trigger circuit is arranged in the second circuit which generates a second voltage pulse as a function of the second tone (B) and that an AND gate is coupled to the first and second trigger circuit, which generates an output voltage when the first and second voltage pulses occur simultaneously gives away.

Further developments and refinements of the invention are the subject matter. Subclaims.

The invention is advantageously used in a selective call receiver in which the decoder responds to two successive tones and triggers a warning tone or call in the call receiver. These pagers comprise a first and a second audio frequency filter, with which the two ring tones are different Frequency can be filtered out. The filters can be used as active filters in the form of integrated Circuits designed or as electromechanical frequency-selective filters be constructed. The ringing tones emitted by the filters are different Frequency are fed to the Ruf ton decoder as a hybrid module from an integrated circuit is built on a thick film carrier. This ringing tone decoder comprises a threshold value detector for each of the two ringing tones, which supplies a voltage to an integration circuit, to the resulting To give control voltage a certain shape. The control voltages are after further processing fed to an AND gate, which supplies an output-side voltage signal when the two received tones in the correct sequence with sufficient amplitude and a certain distance occur between the two ringing tones. Under these conditions the AND gate is activated and delivers the output voltage signal to a warning sound system. The AND gate is biased so that that it remains switched on as long as the second ringing tone is received. It can also be a monostable multivibrator can be provided, which sounds the warning tone for a certain period of time after the end of the second ringing tone sustains There is also a warning tone oscillator with an astable Multivibrator works together and pulsed by this for the delivery of an intermittent Wtrntons will.

To the ringing tone decoder as multicast decoder to use, it is provided with an auxiliary circuit, which is also an integrated circuit to ^c: is constructed nem thick film carrier. This group call decoder is coupled to the second circuit stage of the two-tone sequence decoder and supplies an input signal to the AND gate as a function of the second ringing tone, if this is present for a sufficiently long time. This will cause the warning beep

zillator excited The system can be set up in such a way that when a group tone occurs, a continuous tone A warning tone is generated. It is also possible to use the group call decoder with the two-tone sequence decoder in an integrated circuit on a thick film carrier, so that the resulting hybrid module includes both circuits. The ringer decoder works with a relatively low battery voltage in the order of magnitude between 1 and 1.5 V and is relatively insensitive to voltage fluctuations.

The features and advantages of the invention result can also be derived from the following description of exemplary embodiments in conjunction with the claims and the drawing. It shows

F i g. J is a simplified block diagram for a pager with a decoder according to the invention,

F i g. 2 the circuit diagram of a decoder as a hybrid module is formed using an integrated circuit on a thick film substrate,

F i g. 3 shows a large number of diagrams to explain the mode of operation of the circuit according to FIG. 2,

F i g. 4 the circuit diagram of a second hybrid module, that together with the module according to FIG. 2 can be used for a group call.

The in F i g. 1 illustrated pager with a decoder system according to the invention is included in the block 10 the RF receiver with modulation stages of known type The receiver can be used as an FM receiver or be constructed as a heterodyne receiver, with a local oscillator and mixer being available convert the high frequency to an intermediate frequency. The intermediate frequency becomes demodulation an LF signal obtained, which is fed to an LF preamplifier 11 and an LF amplifier 12. The signal processed in the LF amplifier 12 is fed to a loudspeaker 13 for playback.

The ringing tones are modulated onto the HF frequency and transmitted via the LF preamplifier 11 the sound filters 15 and 16 supplied. These filters can consist of active elements in the form of integrated circuits or be constructed in the form of electromechanical resonance elements, with z. B. a reed relay Can be used. The filtered out tone frequencies are fed to a two-tone sequence decoder 18 which generates a low-frequency ringing tone. This low-frequency ringing tone is transmitted to the low-frequency amplifier 12 via input 14 for playback via the loudspeaker 13. The decoder 18 can also use a direct current control voltage Apply directly to the amplifier via connection 17, with which a squelch operation is possible.

With the two-tone sequence decoder 18, a group call decoder 19 is also connected, with which it is possible is to generate a ringing tone in response to a group call. Decoders 18 and 19 will be below with reference to FIG. 2 and 4 explained in more detail

The circuit of the two-tone sequence decoder 18 is shown in FIG. 2 and can be used as a hybrid module with a integrated circuit on a thick film carrier be trained. The integrated circuit is shown in FIG. 2 shown within the dashed lines on the other hand the thick film carrier comprises the circuit shown within the dash-dotted line of the integrated circuit are as triangular areas and the terminal contact areas on Thick-right carriers are shown as semicircular areas. Circuit elements that are not housed in the hybrid module are indicated outside the dash-dotted line. The circuit is designed so that they can be fed from a battery, the feed voltage fluctuating between 1 and 1.5VoIt can.

According to FIG. 2, the first ring tone A from the filter 15 according to FIG. 1 is applied to the input terminal 20, which is connected to the connection contact surface 1. This first ringing tone A is generated via a capacitor 22

ίο on the thick film carrier on the connection contact surface 14 of the integrated circuit applied, which in a transistor 24 which is conductive in the quiescent state When the transistor 24 is conductive, the level of the ringer is amplified from its collector to the base of a Transistor 25 applied voltage below the turn-on voltage for this transistor so that this in Idle state is not conductive as soon as the tone signal applied to the base of transistor 24 has a certain level Exceeds the peak amplitude voltage, the conductivity of the transistor 24 is periodically in such Reduced scope that its collector voltage rises and is sufficient to periodically turn the transistor 25 to turn on. The circuit construction is such that a DC bias change across the transistor 25 is caused to change the gain of the transistor 24 due to the change in the supply voltage to compensate. This is a threshold stability with respect to changes in the Low voltage supply voltage achieved

The signal present at the collector of the transistor is integrated due to the effect of the resistor 27 and the integration capacitor 28. These integration elements are provided outside of the hybrid module and can be exchanged in order to provide a desired time constant which is adapted to the duty cycle for the ringing tone. The integration capacitor 28 is charged from the voltage supply via the resistor 27 when the transistor 25 is in a state of low conductivity. This voltage is applied to the base of a transistor 30, which keeps it in the conductive state. This transistor 30 is switched off when the integration capacitor 28 is discharged via the transistor 25, ie when the latter becomes conductive due to a first ringing tone A being applied. At the end of the ringing tone, the integration capacitor 28 begins to charge again via the resistor 27 and applies a voltage to the base of the transistor 30 which is sufficiently high to switch it back into the conductive state.

The collector of the transistor 30 is connected to the base of a transistor 32 via a capacitor 31 which is mounted on the thick film carrier. The transistor 32 is conductive in the idle state due to the potential applied to the base from the supply voltage via the resistor 33. If the transistor 30 is made conductive at the end of the first ringing tone A , ground is effective via this transistor and the capacitor 31, so that a strong charging current is drawn via the resistor 33. With the resulting increase in voltage at resistor 33, the potential at the base of transistor 32 drops and controls it into the blocking state. The collector voltage of the transistor 32 thus rises to a value in the order of magnitude of the supply voltage B +, whereby this transistor 32 is switched off for a short time, which results from the values of the capacitor 31 and the resistor 33

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According to FIG. 2, the second ringing tone B is applied from the filter 16, according to FIG. 1, to the terminal 35 and from this via the contact pad 12 and via a capacitor 36 to the contact pad 8 of the integrated circuit together with the transistor 39 forms an amplifier and threshold value detector which works in the same way as the corresponding circuit of the transistors 24 and 25 for the first ringing tone A. The collector of the transistor 39 is connected to an integration circuit of the resistor 40 and the capacitor 41 . This integration circuit can have a shorter time constant than the integration circuit composed of the resistor 27 and the integration capacitor 28 for the first ringing tone A , since it is not necessary. delay the second ring B , as explained below. The voltage on capacitor 41 acts on the base of a transistor 42, which is conductive in the idle state The collector of this transistor 42 is therefore in the idle state at a low voltage above ground potential, which is the saturation voltage of transistor 42 when the second ringing tone B received becomes, this makes the transistor 39 conductive, whereby the capacitor 41 discharges through the transistor 39 and the transistor 42 turns off. The collector voltage of the transistor 42 rises as a result.

A series UN D gate is also provided, which is enclosed. A ringing tone A trigger circuit and a ringing tone ß trigger circuit become effective. The ringing tone A trigger circuit comprises the transistors 25 and λθ, while the ringing tone ß trigger circuit comprises the transistors 39 and 42. The AND gate comprises the transistors 45 and 46 which are connected to one another and to the resistors 47 and 48 between the supply voltage B + and ground are connected in series. If the transistor 32 is switched off when responding to the first ringing tone A , so that a voltage pulse is generated at its collector, this causes a switch-on voltage at the base of the transistor 45. In the same way, when the transistor 42 is switched off by the second ringing tone B, a voltage pulse is applied whose collector develops, which turns on transistor 46. Thus, the current path to transistor 45 is completed so that it becomes conductive. Correspondingly, through simultaneous trigger pulses generated as a function of the first and second ringing tones A and ß, the series circuit with the transistors 45 and 46 becomes conductive, so that a current flows through the resistors 47 and 48 The resistor 48 is much smaller than the resistor 47, so that the voltage applied to the base of the transistor 50 drops to a value at which this transistor becomes conductive. The conductive transistor 50 applies the supply voltage B + to the terminal 17, which is connected to the LF amplifier 12 according to FIG. 1 can be connected to switch on this amplifier. This voltage potential also causes an alarm call to be switched on, as described below.

To explain the mode of operation of the trigger circuits and the AND gate, the diagrams according to FIG. 3 provided. Diagram a shows the first ringing tone A and the second ringing tone B, which are used for the selective operation of the paging receivers. The first call ton A has a first frequency and can be present for a duration in the order of magnitude of 1 second. The second ringing tone B has a second frequency and can be present for a duration of the order of 3 seconds. A short intermediate interval can be of the order of magnitude of about 300 milliseconds and runs from the end of the first ringing tone A to the beginning of the second ringing tone B. However, such an intermediate interval is not necessary for the operation of the decoder. For the ringing tone system described, frequencies in a relatively wide band can be used for the individual ringing tones, and it may be desirable to place the band in a frequency range between 50 and 200 Hz so that it is below the speech frequencies to be transmitted. However, it is also possible to move the band to a frequency range that is above the voice frequencies to be transmitted.

Diagram b shows the voltage at the collector of transistor 30. Since this transistor is conductive in the quiescent state, the collector voltage is initially at a value which is slightly above ground and which corresponds to the saturation voltage of transistor 30. Before the start of the first ringing tone A , the integration capacitor 28 is charged. With the beginning and duration of the first ringing tone A , the integrating capacitor 28 is discharged through the conductive transistor 25 until it reaches a voltage value which is low enough to switch the transistor 30 off. The time to discharge the capacitor to this value is marked in diagram b as b \ . This delay time is used to protect against false displays due to noise or interference signals of short duration that may be present. When the first ringing tone A 2u is over, the transistor 25 switches off. so that the integration capacitor 28 can be charged via the resistor 27. As soon as the charge of the capacitor has reached a certain value, the transistor 30 is switched on again, which means that the collector circuit drops to the saturation value again.The time required to charge the integration capacitor 28 to a voltage value sufficient to switch on the transistor 30 is indicated in diagram b by 62 Die Operation of transistor 32 is described by diagrams c and d . As already mentioned, the transistor 32 is conductive in the idle state, since the voltage applied to its base via the resistor 33 keeps the transistor in the conductive state.This voltage is shown in diagram c . When the transistor 30 is switched off, the charge in the capacitor 31 increases slightly and thus accordingly increases the voltage at the base of transistor 32, as indicated by the pulse el. When the transistor 30 is switched on again, a charging path builds up via the capacitor 31 and the resistor 33, which results in a larger voltage drop across the resistor 33 and the voltage at the base of the transistor 32 drops accordingly. This is indicated by the pulse dZ . This voltage drop switches off the transistor 32, so that the voltage at its collector rises to the value indicated by the pulse in diagram d to the value of the supply voltage S + when the transistor is switched on. This voltage drops again at the point in time d1 to the saturation value, the point in time of this drop being determined by the values of the resistor 33 and the capacitor 31

509529/22

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The dashed line drawn in diagrams c and d indicates the conditions when the second ringing tone B follows the first ringing tone A in the case of a received selective call.

The diagram e according to FIG. 3 describes the function of the ringing tone B trigger transistor 42. This transistor is conductive in the idle state, so that its collector voltage corresponds to the saturation value. The time constant of the integration circuit for the second ringing tone B is set such that the transistor 42 is switched off before the generation of the pulse at the collector of the transistor 32 for the first ringing tone A. This disconnection of the transistor 42 has the effect that the collector voltage increases at the time el, whereby the transistor 46 of the series AND gate becomes conductive. When the transistor 32 is then switched off in order to make the transistor 45 conductive, a voltage is applied to the base of the transistor 50 via the series circuit with the transistors 45 and 46 and the base of the transistor 50 is switched on. The conductive state of this transistor 50 is described by the diagram / '. This turns on the NF amplifier, as mentioned above.

In Fig. 2 also shows an astable multivibrator 51 made up of transistors 52, 54 and 56. These transistors are connected to a further transistor 58 which is located in the direct current path of the multivibrator and controls it. The base of the transistor 58 is connected to the collector of the transistor 50 via a resistor 59. When the transistor 50 is switched on as a function of the ringing tone A trigger voltages and the ringing tone ß trigger voltages, the transistor 58 also becomes conductive and switches the astable multivibrator on. The cycle time of the multivibrator 51 is determined by a capacitor 53 which is connected between the emitter of the transistor 52 and the emitter of the transistor 54. The capacitor is connected via the connection contact surfaces 5 and 7 of the thick film carrier and the connection contact surfaces 5 and 7 of the integrated circuit. The capacitor 53 is connected as an external circuit element, so that the period duration of the multivibrator can be changed in a simple manner.

The multivibrator 51 controls the warning sound oscillator 60. that consists of the transistors 61,6Z 63 and the double-T filter 65 is formed. The transistors 61, 62 and 63 are part of the integrated circuit, whereas the Double-T filter 65 arranged on the thick film carrier is. The astable multivibrator 51 controls the oscillator 60 via the transistor 68, which acts as an inversion stage in order to switch the warning sound oscillator on and off. The warning tone is sent to the connection contact surface 2 of the integrated circuit and via a con capacitor 70 to you. Terminal contact surface 4 of the thick film carrier applied From there he can connect the LF amplifier 12 of the recipient according to FIG. 1 are supplied to reproduce the warning tone in the loudspeaker 13. The structure of the wam sound is shown in FIG. 3 described by the diagram ^.

It is desirable to keep the warning tone oscillator switched on for a period of time during which the second ringing tone B is received. To achieve this, it is necessary that the two transistors 45 and 46 of the series AND gate are in the conductive state The transistor 46 is kept in the conductive state by the ringing tone S trigger voltage from the transistor 42, however, as shown in FIG. 3 it can be seen that the transistor 32 is only kept in the switched-off state for a short time by the circuit which responds to the first ringing tone A. In order to keep the transistor 32 is also turned off during the second ringing tone Bim state, a latch circuit is provided to the transistor 72nd This transistor 72 becomes conductive when transistor 50 conducts and causes the voltage across resistor 33 to drop to a value at which transistor 32 is switched off.

ίο This means that the transistor 45 remains in the conductive state. The warning tone is thus made available as long as the second ringing tone B is received. This is in FIG. 3 in diagram d between times di and (ß the case. The same applies to the assigned time segments of diagrams e, and g.

In order to provide an indication from which it can be seen that the pager is working properly, it is provided that the warning sound oscillator is energized when the pager is switched on. The capacitor 29, which lies between the emitter and the collector of the transistor 30, begins to charge when the supply voltage B + is applied. This turns transistor 32 off to provide the turn-on bias for transistor 45 of the series AND gate. The transistor 46 also becomes conductive, since the charging capacitor 41 keeps the transistor 42 switched off, so that a current flows through the series circuit of the resistors 47 and 68 and the transistor 50 switches on. The supply voltage B + is thus transmitted from the collector of transistor 50 to terminal 17, which is connected to LF amplifier 12. The voltage transmitted via terminal 17 is used to switch on the LF amplifier, with the same voltage being used at the same time

of the warning sound oscillator, as already mentioned. use bark. The transistor 50 remains in the conductive state for a short time, this period of time from the Time constant of resistor 40 and capacitor 41 is determined.

It may be desirable to leave the warning tone oscillator switched on for longer than the duration of the second ringing tone B corresponds. To achieve this, a monostable multivibrator is provided in the integrated circuit. This monostable

Multivibrator includes transistors 74, 75 and 76 as well the transistor 77 connected as a diode. A capacitor 80 is connected on the one hand to the collector of the transistor 50 via the connection contact area 10 of the integrated circuit and the connection contact areas 9 of the thick film carrier and, on the other hand, to the base of the transistor 74 via the connection contact surface 6 of the thick-film carrier and the integrated formwork. This capacitor 80 becomes elongated discharged when transistor 50 is turned on

being the voltage at the collector of the transistor 50 is transferred to the base of transistor 74. the Transistors 74 and 75 share the current from the transistor 76 ^ When the ao-applied to the base of transistor 74 Voltage is the reference voltage at the base of the

If it exceeds transistor 75, it becomes conductive and, as a result, shadows transistor 75. This increases the voltage at the collector of this transistor 75 and acts on the base of the transistor 82, which thus becomes conductive. This transistor 82 is parallel to the transistor Γ, ³ , ΐ ^ ^{with the} transistor 45 hn frame of the Senen-AND gate together in order to keep the transistor 50 in the conductive state. As long as the transistor 45 has the latching circuit with the transistor 72 in the

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is kept conductive state, the AND gate remains conductive until the transistor 82 is turned off. The capacitor 80 charges through the conductive transistor 74, so that the voltage at the base of the transistor 74 drops below the voltage value which is required to keep the transistor 74 in the conductive state. This switches off the warning sound oscillator. This additional duration of the warning tone is shown in the diagram / ″ between the times / 2 and / 3 or in the diagram g between the times g2 and g3 The use of the transistor 76 in the emitter circuit of the transistor 74 has the effect that the impedance at the terminal pad 6 is very large, so that very long time intervals are obtained relatively easily.

In Fig. 2 are also the connections for the group call decoders 19 designated and effective Auxiliary circuits shown, its circuit diagram in detail in Fig. 4 is shown. The terminal contact surfaces of the group call decoder through which the Connection to the circuit 2 takes place, are provided with the same reference numerals in both figures. This Group call decoder can also be used as a hybrid module with an integrated circuit on a thick-film carrier be constructed and is shown in this way in FIG. 4 shown

The connection contact surface 5 of the group call decoder 19 according to FIG. 4 is connected to the connection contact area 8 of the decoder according to FIG. 2 connected. If no second ringing tone B is received, a voltage is transmitted from the connection contact area 5 to the connection contact area 1 of the group call decoder. This voltage is further transmitted via a resistor 85 to the base of a transistor 86 and keeps this transistor in the conductive state. The transistor 87 is thus switched on to a current path, since its collector is connected to the supply voltage via the resistors 88 and 89. The transistors 86 and 87 are connected in parallel to the capacitor 90 which is in series with the resistor 88 and 89 between the supply voltage β + and ground. When a second ringing tone B is received, the voltage applied to the input of the multicast decoder drops to a lower value and turns transistor 86 off. As a result, a parallel branch is switched on via the transistors 86 and 87 to the capacitor 90 so that this capacitor, which was previously held at an output voltage determined by the collector voltage of the transistor 87, begins to charge via the resistors 88 and 89 and its voltage is transferred to the base When the capacitor 90 has reached a sufficiently high voltage, the transistor 91 is switched on so that its collector voltage drops. This collector voltage acts on the base of the transistor 92 and switches it off with decreasing voltage. Once this transistor is turned off 92 and its collector voltage rises Toggle te, this acts on the base of the transistor 94 and the transistor 95 and turns on the two transistors in the conductive state.

The collector of the transistor 94 is above the connection contact surfaces 5 of the integrated circuit and 6s the connection contact surface 2 of the thick film carrier of the group call decoder to the connection contact surface 10 of the thick film carrier and the connection contact surface 11 of the integrated circuit of the two-tone sequence decoder and thus to the base of the transistor 32 connected. The base of transistor 32 is thus switched to ground and transistor 32 is switched off. The rising collector voltage of this transistor switches on the transistor 45 of the series AND gate. Since the second ringing tone B is received, the transistor 46 of the AND gate is switched on, so that the switching on of the transistor 45 causes the AND gate to render the transistor 50 conductive. This causes the astable multivibrator to energize the warning sound oscillator as described above.

The collector of the transistor 95 of the group call decoder 19 is connected via the connection pad 6, a resistor 96 and the connection pad 3 to the two-tone sequence decoder, via the connection pad 7 and thus to the emitter of the transistor 52 of the astable multivibrator. The voltage supplied via this connection interrupts the astable multivibrator so that it no longer excites the warning sound oscillator. A group call is accordingly obtained in that a second ringing tone B aüein is present for a longer period of time than corresponds to a normal, selective call. Such a period of time can e.g. B. 5 seconds, so that in this case the group call announcer turns on the series AND gate and energizes the warning tone oscillator. As long as the oscillator is working continuously, a group call can be distinguished from an individual call.

The time constant of capacitor 90 and resistors 88 and 89 is such that the voltage across capacitor 90 is not sufficient to turn transistor 91 on before the tone sounds for a period of e.g. B. 5 seconds so that the group call is not triggered with a normal, selective call. This prevents the group call from being triggered by the second ringing tone B alone during normal, selective calls. The duration of the second ringing tone B for a group call is stabilized in the event of fluctuations in the supply voltage by an offset change in the charging time due to the changes in the supply voltage, in that the initial voltage at the capacitor 90 is changed. This eliminates the need to send out a relatively long group call, thereby avoiding an excessively long channel occupancy

The decoder circuit described above has proven to be extremely stable and is particularly advantageous for the use of miniature paging receivers. Since it is constructed as a hybrid module with an integrated circuit, both the decoder and the warning sound oscillator and the controls required for this can be made very small. It is possible to use the two-tone sequence decoder alone or in conjunction with the group call decoder. The described decoder according to the invention operates with a two-tone sequence for the call signal, with two tones of specific frequencies. Find amplitudes and certain keying use. The decoder only responds to such signals. Since the circuit is essentially designed as an integrated circuit, however, the Schaltkreisele elements that determine the duty cycle are arranged outside of the integrated circuit, the decoder can be used for different call systems. The decoder circuit comprises a series

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AND gate that excites a warning tone oscillator depending on tones of certain frequencies and duration Decoder transformed into a Gnippenr.if decoder which responds to signals for a relatively long time. The warning tone can be intermittent or they can also be delivered continuously and with varying periods of time.

For this purpose 3 sheets of drawings

Claims (1)

Patentv4> Proverbs: 1. Ringing tone decoder that responds to a first and a second ringing tone of different frequency, which are received one after the other, with a first circuit for receiving and selecting the first tone, a second circuit for receiving and selecting the second tone, a Integration stage with resistor and capacitor and a blocking circuit to prevent the emission of a warning tone without a first ringing tone, characterized in that the integration capacitor (28), which is initially charged to full voltage, is passed through a transistor (25) which responds to the first tone ( a) is responsive, during the duration of the first tone (a) discharges and recharges after the decay of the first tone (a) that mi, the Integntionskondensntor (28) comprises a first trigger circuit (30,31, 32,33), which in the first circuit is arranged coupled that the trigger circuit (30, 31, 32, 33) generates a first voltage pulse as soon as the voltage of the integration skondensators (28) after the first tone (A) has risen to a certain value that a second trigger circuit (39,40, 41, 42) is arranged in the second circuit, which depending on the second tone (B) a second voltage pulse is generated and that an AND gate (45,46) is coupled to the first and second trigger circuit. which emits an output voltage when the first and second voltage pulses occur simultaneously. 2. Ringing tone decoder according to claim 1, characterized in that the AND gate consists of a first (45) and a second (46), series-connected transistor and a transistor (50), which emits the output voltage when the first and the second transistor (45.4vi) are conductive. 3. Ringing tone decoder according to claim 1 or 2, characterized in that a transistor (72) is connected to the transistor (50) and the first circuit which extends the first voltage pulse to the period of time during which the transistor (50) operates . 4. ringer decoder according to claims 1 to 3, characterized in that with the transistor (50) a warning sound oscillator (60) is connected. which depends on the output voltage Warning tone generated. 5. ringer decoder according to claim 4, characterized in that a multivibrator (51) is provided which connects the transistor (50) with the warning sound oscillator (60) to an intermittent To effect operation of the warning sound oscillator. 6. Ruf tone decoder according to claims 1 to 5, characterized in that an auxiliary circuit (19) is coupled to the second circuit, which is a function of the second tone (B) when this is maintained for a given period of time third voltage pulse generated that the auxiliary circuit (19) is coupled to the first circuit, that the third voltage pulse causes the first circuit to emit a first voltage pulse, so that the AND gate (45, 46) emits its output voltage even if only the second tone (B) alone as a group call Will be received 7. Ruf decoder according to claim 6, characterized in that mh the auxiliary circuit (19) and the warning sound oscillator (60) is another circuit (51) is coupled to an intermittent operation of the warning tone counter when the first (A) and the second (B) tone are received consecutively, and continuous operation when only the second tone is received (Β} if this is for one ίο given period of time is maintained 8. call decoder according to claim 6, characterized in that the detection of the group call by discharging an integration capacitor (90) initially charged to full voltage in the group call decoder (19) 9. Ruf decoder according to claims 1 to 8, characterized in that the transistor (25) responsive to the first tone (A ) in the first circuit only reacts to a tone with a minimum amplitude appeals to. ία Ruf decoder according to claims 1 to 9, characterized in that a capacitor (29) is arranged in parallel with the first trigger circuit is. which occurs when the operating voltage is switched on (B +) charges slowly and thus briefly simulates the presence of a first tone (A) while the second tone (B ) is simulated by the integration capacitor (41), which is also slowly charging, so that an output voltage appears briefly at the AND gate that causes the Warning sound oscillator makes. 11. Ruf decoder according to claims 1 to 10, characterized in that for the extension of the warning tone on the decay of the second tone (B) a monostable multivibrator (74,75,76,77, 80, 82) is provided, which works together with the AND gate 12. Ruf decoder according to claims 1 to 11, characterized in that it is used as a semiconductor device is built on a thick film substrate and that the time-determining components are arranged outside of the semiconductor circuit.