DE1205588B - Device for the selective generation of electrical AC switching criteria for telephone subscriber stations - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. α .:

Number:
File number:
Registration date:
Display day:

H04m

German KL: 21 a3 -16/10

S 93523 VIII a / 21 a3
September 30, 1964
November 25, 1965

The subject of the patent application S 91075 Villa / 21 a ³ is a device for the optional generation of electrical alternating current switching criteria of different frequencies for telephone stations, in particular for the generation of coded audio frequency selection criteria with two electroacoustic transducers consisting of the microphone and the telephone of the subscriber station, which are electrically in Connected in series and acoustically coupled to a resonator whose natural oscillation characteristics can be changed to form an acoustic oscillator, the stimulated oscillations of which are impressed according to the natural oscillation characteristics set on the resonator at a certain frequency, which is converted into an alternating current corresponding to a frequency that can be evaluated as an alternating current switching criterion.

The object of the invention is to provide the calling organs with such a device which is used for frequency selection to replace the subscriber station.

It is known that the incoming call signal stream is transmitted through the handset instead of by an alarm clock or to make the loudspeaker of the station audible. But here is the Difficulty, if the calling frequency is directly applied to the receiving transducer, a sufficient one Generate volume. While at low frequencies, e.g. B. 25 Hz ringing frequency, the Converter efficiency and hearing poor higher frequencies, e.g. B. 2000 Hz, because of the risk of crosstalk on other subscriber lines cannot be transmitted at the required level.

To avoid this crosstalk, it is already known to use the incoming low-frequency Rectify ringing current and with this its own generator for higher-frequency alternating currents to stimulate which are made acoustically effective in the listener.

In telephone stations which use a device according to the main patent application for generating audio-frequency alternating current switching criteria, additional generators, amplifiers for receiving calls and the like can be saved according to the invention and this device can thus be used for a further function the two transducers, the resonator and the amplifier existing electroacoustic oscillators can be connected to the incoming ringing current rectified by a rectifier and with its energy emits the call signal. This ensures that an incoming low-frequency paging device can selectively generate
AC electrical switching criteria for
Telephone subscriber stations

Addition to registration: S 91075 VIII a / 21 a3 Auslegeschrift 1201416

Applicant:

Siemens & Halske Aktiengesellschaft,

Berlin and Munich,

Munich 2, Wittelsbacherplatz 2

Named as inventor:
Josef Finkl, Munich

current without affecting other subscriber lines through the existing electroacoustic Schwinger is converted into an acoustically favorable frequency. As both for the Submission of the selection criteria as well as for the conversion of the incoming low-frequency ringing current an amplifier of relatively low power is sufficient, for this can be the case with telephone stations frequently used microphone amplifiers can be used. A clearly audible call signal can So in such telephone stations with largely already existing components and can be generated with a low-frequency ringing current without significantly changing the station circuit. In the following the invention is explained in more detail with reference to an embodiment shown in the drawing. It means

F i g. 1 is a schematic representation of the frequency selection device in ringing current receiving circuit and

F i g. FIG. 2 shows a circuit for a telephone station with the device according to FIG. 1.

In Fig. 1 shows the device for the optional generation of electrical AC switching criteria, which consists of two electroacoustic transducers 1 and 2, of which the transducer 1 through a microphone capsule and the transducer 2 is formed by a telephone capsule. Acoustically

509 739/80

I 205

the two transducers 1 and 2 are coupled via a resonator 3 to form an acoustic transducer 1-3, the natural frequency of which can be changed by openings 4 which can be optionally covered. The converters 1 and 2 are arranged in a handset 5 shown in dashed lines and are on the electrical side through an amplifier6 and a transformer? connected in series. This electro-acoustic transducer works like a feedback generator, which oscillates at the frequency for which the feedback condition applies is satisfied. With appropriate dimensioning, the generated frequency becomes predominant of the respective natural frequency which can be set by closing one or more openings 4 of the resonator 3 and is removable as a selection criterion at the connection point 8.

When the handset 5 is in place, the device is via a contact 9 of a changeover switch 10 connected to a connection point 11, via which the incoming, rectified ringing current is lower Frequency is fed. This excites the electroacoustic sound formed by elements 1, 2, 6 and 7 Oscillator whose vibrations are modulated according to the setting of the resonator 3 amplified by the amplifier 6 and radiated from the resonator 3. This modulation can be adjusted in to the surrounding noise conditions by closing the corresponding openings 4 in the placed state of the handset 5 can be optimally adjusted. When the handset is removed 5 the contact 9 is opened and a contact

12 of the switch 10 closed, via which, as described above, the delivery of the with the selector generated alternating current switching criteria takes place.

F i g. 2 shows the station circuit. Instead of an alarm clock, there is a filter capacitor between the a-, & -wires of the telephone subscriber line

13 having, designed as a full wave rectifier rectifier 14 connected. The rectifier 4 is via the switch 10 designed as a hook switch with the microphone 1 and connected in parallel to a resistor 15. Telephone 2, microphone 1 and amplifier 6 are in connected to the transformer 7 in the usual manner. The filter capacitor 13 has a low ohmic resistance, and the resistor 15 is high resistance, so that in the illustrated Switching position a largely asymmetrical load on the transformer 7 comes about, which makes the back loss almost ineffective. As shown in dashed lines, a corresponding Contact of the switch 10, the resistor 15 is switched off when the handset 5 is in place so that the back loss is completely switched off. As for the amplifier 6 such low power is sufficient, a conventional microphone amplifier can be used to amplify speech is already built into many telephone stations.

As can be seen, the existing components 1 to 3, 6 and the Transmitters 7 that are customary in station circuits are also used. Instead of an alarm clock, only the smaller rectifier 14 is used. Such a device can thus be installed in a station housing usual dimensions easily accommodate. For the sufficiently loud and low-frequency call signal is neither a tone-frequency ringing current, which with a sufficient level only poorly over the line can be transferred, but the arrangement of a separate generator is necessary. The one that is in itself simple device for generating alternating current switching criteria also replaces those otherwise used for the Call signal delivery necessary components in the station and requires despite this dual function no significant change in the station circuit itself.

Claims (2)

Patent claims: ! .Device for elective generation of electrical alternating current switching criteria of different frequencies for telephone stations, in particular for the generation of coded audio frequency selection criteria with two electroacoustic transducers consisting of the microphone and the telephone of the subscriber station, which are connected electrically in series via an amplifier and acoustically with one in its Natural oscillation characteristics of changeable resonator are coupled to an acoustic oscillator, whose stimulated oscillations according to the natural oscillation characteristics set on the resonator are impressed with a certain frequency, which is converted into an alternating current of the corresponding frequency that can be evaluated as an alternating current switching criterion, according to patent application S 91075 VIII a / 21 a », characterized in that the electroacoustic oscillator consisting of the two transducers (1, 2), the resonator (3) and the amplifier (6) is connected to the incoming, from a Gleic Hrichter (14) rectified ringing current can be switched on and with the energy of which the call signal is emitted. 2. Apparatus according to claim 1, characterized in that the connection of the electroacoustic Oscillator for the incoming call flow via a per se in the subscriber station existing transformer (7) takes place. 1 sheet of drawings 509 739/80 11.65 © Bundesdruckerei Berlin