DE1185666B - Circuit arrangement for key-controlled transmission of alternating current signals, in particular for key dialing in telephone subscriber stations - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Boarding school Class: H 04 w

German class: 21 a3 - 16/10

Number: 1185 666

File number: T 24965 VIII a / 21 a3

Filing date: October 26, 1963

Opening day: January 21, 1965

With the key-controlled transmission of alternating current signals in a specific frequency code It is desirable that the simultaneous actuation of two buttons does not result in false AC signals sent out and accordingly also evaluated in the receiving device. Is it namely to the touch dialing in telephone subscriber stations, which by transmission of alternating current signals is carried out in a certain frequency code, so it is with the simultaneous accidental actuation of two buttons possible due to incorrectly formed dialing signals an activation of undesired participants takes place or that at least central one Control elements in the switching device are unnecessarily occupied.

The aim of the invention is therefore to activate two buttons at the same time to send out a signal that clearly differs from the normal switching indicator, which is in the Evaluation device gives the possibility to recognize the wrong operation of the keyboard and thereby to prevent the evaluation of the incoming signals.

The invention, which relates to a circuit arrangement for key-controlled transmission of alternating current signals in the "n-off / n" frequency code, solves this problem in that, by appropriately classifying the contacts actuated by the selection keys assigned to the individual signals, into the switch-on and / or frequency-determining circuits of the frequency generator to generate the alternating current signals when two buttons located next to or on top of each other in the keypad are pressed at least η + 1 frequencies are transmitted and switching means provided in the receiving station prevent the evaluation of these frequencies when more than η frequencies are received. A plurality of frequency generators are expediently provided, and the selection keys lying next to one another in a row and one above the other in different rows each control a different frequency generator. The individual frequency generators are each suitable for generating one of several different frequencies, the selection of which is made by contacts of the actuated selection buttons. It is also advantageous, in order to standardize the structural units, that the same frequencies can be generated by all frequency generators. If the code »2 out of 5« is used as the selection code, three frequency generators suitable for generating each of the five frequencies are provided.

Circuit arrangement for button-controlled
Emission of alternating current signals,
especially for touch dialing in
Telephone subscriber stations

Applicant:

Telephone construction and normal time G. m. B. H.,

Frankfurt / M., Mainzer Landstr. 134-146

Named as inventor:

Ewald Kiebler, Kronberg (Taunus);

Arthur Kessler, Frankfurt / M.

With the code "1 out of 10", that is, with an arrangement in which a special code is used for each individual dialing code Frequency is used, the arrangement is expediently made so that two oscillators are interconnected so that they are used for both the normal loop current of the telephone station as well as for the oscillator current flowing when one or two keys are pressed are. The decoupling windings of both oscillators must also be connected in series in this case. It must be ensured that only one oscillator oscillates when a key is pressed, although both Oscillators receive power. This can be achieved in a simple manner in that in the oscillators Transistors of different conductivity types are used.

Exemplary embodiments of the invention are shown in the drawing. It shows

F i g. 1 a push-button dialing station for the transmission of tone-frequency dialing signals in the code "1 out of 10" in a familiar Execution form,

Figure 2 shows the same station using the same frequency code according to the invention and

F i g. 3 and 4 the schematic representation of a keypad and the breakdown in table form the individual oscillators and the individual frequencies to be generated by these oscillators in With regard to the individual keys of a ten-part keyboard.

In Fig. 1, the transmission line alb in the idle state of the hook switch contact Hu is alternating current via the alarm clock W of a remote

409 769/96

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Subscriber station closed. If the listener becomes permeable, so that the oscillators pick up current from the hook Hu , then the loop is held. However, only that oscillator oscillates, direct current via the windings of the transformer Ü with which a key is pressed, because the resonant circuit and the series-connected break contacts of the other oscillator through the large condensers TlO, which are actuated by the ten-part keyboard 5 capacitors Cl and CII or .CII and CIV can each be short, closed. To the transformer Ü is closed.

are in a known manner in backheard-free circuit Are the ten keys in one of the listener H and the microphone M in the keypad with the connection row next to each other and two adjacent ones of a replica JV are coupled. The arrangement of keys operated at the same time is ensured by the Verteizur emitting the dialing code consists of io development of the individual dialing codes on the two an audio frequency oscillator To, the transistorized oscillators O1 and O 2 that is designed in each and in a known manner. The frequency oscillator generates one frequency each, and thus two of these generators To are essentially emitted by the frequencies. The receiving inductance of the coil Wl and the capacitance Cl device, which is not shown, only needs to be determined up to ClO. By pressing the key con- 15 to be designed so that when two clocks Tl to TlO are received, one or more condensate frequencies can cause a corresponding fault signaling sators Cl to ClO in the frequency-determining circuit and the evaluation of these frequencies can be switched to the oscillator To, to prevent that. Such devices are generally known for the frequency generated by this oscillator. Reception of audio-frequency signals.
frequency-determining circuit of the oscillator To, If the individual dialing codes are sent out when the key contact T 9 is pressed, the frequency code "2 out of 5" is used, i.e. when capacitors C 9 and ClO are connected in parallel, one of the ten dialing codes is transmitted in the frequency-determining circuit of the generator To 25 each two frequencies out of five possible Freliegt. sequences sent out, are for this purpose according to the

The coupling of the audio frequency oscillator To tabular compilation according to Fig. 4 three

to the transmission line takes place via the Zener oscillators O I, OH and OHI, which im

Diode Z, while the speech currents via the con-essentials such as the oscillators Ol and Ol of

Capacitors Cl 'and C 2' on the audio frequency oscillator 30 Fig. 2 are formed. Each of these oscillators OI,

be escorted by. The capacitor C 2 'is also OII and OIII can be switched on accordingly

bridged by a resistor R. of frequency-determining capacitors via the

If, in the arrangement according to FIG. 1, each of the five individual and two key contacts are pressed by simultaneous frequencies / 0, / 1, / 2, / 4 or / 7, actuation of two adjacent keys is brought about. Like F i g. 4 reproduces, the assignment opens, so for example the two key contacts of the individual key contacts to the frequency T 9 and TlO, then the transmission of one of the determining capacitors and the frequency corresponding to the oscillator keyTlO, because only torenOI, OH and Olli so taken that, for example, the capacitor ClO is in the frequency-determining manner when the key Tl is pressed through the circuit of the transistor oscillator To . If the oscillator OI wanted the frequency / 0 and the telephone subscriber concerned with the oscilloscope wanted only the lator Oil to transmit the frequency / 1. When pressing key T 9 , he now receives by pressing key T 2, by pressing the oscilloscope key T10, a wrong connector OI is transmitted and the frequency / 0 is transmitted, because instead of the identifier of the choice Oscillator Olli the transmission of the frequency / 2. digit 9 is now the indicator of the dial digit 0 45 If the keys T1 and T2 are not sent out at the same time. is pressed, three friends are sent

This can sequence / 0, / 1 and / 2 by an arrangement according to FIG. 2, so that the evaluation device

be prevented. at the arrival of three frequencies recognizes that

The structure of the subscriber station in FIG. 2 ent- the key has been pressed incorrectly because

Every single dialing code usually only speaks perfectly to that of the subscribers 50

station in Fig. 1, with the exception that in place of two frequencies and at least two

of an oscillator To two oscillators Ol and O 2 frequencies is marked.

are provided. Both oscillators are in the same way. Pressing the

Wise constructed and each have a transistor T1 button T 3 to transmit the frequency / 1 through

and T2 as well as a frequency-determining circuit, 55 the oscillator Oil and the frequency / 2 through the

from the inductances of the windings Wl or oscillator Olli. In this case, too, occurs at

Wl and the button contacts Tl to Γ9 of the simultaneous actuation of the buttons T2 and T3

or T 2 to TlO selected capacitors Cl emit three frequencies, namely the frequency

until C 9 or C 2 to ClO is formed. The oscillations / 0, / 1 and / 2.

tor Ol only contains key contacts of odd- 60 As can be easily seen from a consideration of FIG.

numerous keys T1 to T9, while the oscillator can be known, ensures the selected

O2 through key contacts of the even-numbered key division of the individual individual frequencies on the

T 2 to T10 is controlled. In addition, the keys pressed and the selection of the corresponding

Transistor T2 of the oscillator O2 has a complementary oscillator OI, OII and Olli that with each

Tary conductivity to that of the transistor Tl 65 actuation of two adjacent keys

in the oscillator 01. three frequencies instead of two frequencies for

If one of the ten keys is pressed, the transmission will arrive, so that in any case the

Loop current interrupted, and the Zener diode Z incorrect key actuation can be detected.

To avoid longer key strips, it is often customary to use the keyboards in the form shown in FIG. 3 obvious way to be arranged, ie to provide two rows of keys, of which the upper row of keys contains the keys T1 to T5 and the lower row of keys contains the keys Γ 6 to TlO. With this arrangement, care must be taken that when two buttons located next to one another are pressed simultaneously, that is, when two buttons located one below the other are pressed at the same time, no incorrect dialing code is evaluated. This is ensured in the arrangement of FIG. 3 in that the individual keys Tl, / 4 / assigned apparent from Fig. 3 single frequency / 0, / 1, / 2 to Γ10 or 7, the generation of the by appropriately switching Oscillators OL Oil or Olli takes place. If, for example, the key Γ1 is depressed, the oscillator OI generates the frequency / 0 and the oscillator O Π generates the frequency / 1, as already shown in FIG. 4 has been described. When the key T 6 is depressed , the oscillators Oil and Olli become effective, namely the frequency / 4 is generated by the oscillator OH and the frequency / 2 is generated by the oscillator Olli and transmitted to the line. When the keys T1 and T 6 are pressed simultaneously, the frequencies / 0, / 1, / 2 and / 4 are transmitted, that is, four frequencies are transmitted instead of two frequencies, and the receiving device can arrive at more than two frequencies determine that the key press must be incorrect. Even when the two adjacent keys T 6 and Tl are operated simultaneously, four different frequencies are transmitted and thus the unambiguous identification of an incorrect key operation. In the arrangement according to FIG. 3, this is always the case when two keys lie next to one another within a row or when keys in different rows that lie one above the other are operated simultaneously.

Claims (8)

Patent claims: 1. Circuit arrangement for key-controlled transmission of alternating current signals in the »n-off / n« frequency code, especially for touch dialing in telephone subscriber stations, g e k e η η - 40 45 is characterized by such a classification of the contacts actuated by the selection keys assigned to the individual signals in the switch-on and / or frequency-determining circuits of the frequency generator that at least η + 1 frequencies are transmitted when two keys next to and / or above each other in the keypad are pressed and switching means provided in the receiving station prevent the evaluation of these frequencies when receiving more than η frequencies. 2. Circuit arrangement according to claim 1, characterized in that a plurality of frequency generators (ΟΙ, Ο 2; Fig. 2) are provided and Option keys lying next to one another in a row and in different rows one above the other each control a different frequency generator. 3. Circuit arrangement according to claim 1, characterized in that each of the frequency generator (Oil, O2) suitable for generating one of several different frequencies is. 4. Circuit arrangement according to claim 1 to 3, characterized in that all frequency generators can generate the same frequencies. 5. Circuit arrangement according to claim 1 to 4, characterized in that when using the Selection codes »2 out of 5« three frequency generators suitable for generating each of the five frequencies are provided. 6. Circuit arrangement according to claim 1, characterized in that two frequency generators (oil, O2) are connected together so that they are connected in series both for normal loop current and for the oscillator current flowing when one or two keys are pressed, the decoupling windings ( Wl, W 2) are also in series. 7. Circuit arrangement according to claim 6, characterized in that upon actuation of only one oscillator effectively oscillates with one key. 8. Circuit arrangement according to claim 6 and 7, characterized in that transistors (T1, T2) of different conductivity types are used in both frequency generators. 1 sheet of drawings 409 769/96 1.65 © Bundesdruckelei Berlin