DK159355B - WIRELESS PHONE DEVICE - Google Patents

Description

in

DK 159355 B

BACKGROUND OF THE INVENTION The present invention relates to a wireless telephone apparatus and a stationary exclusively to the telephone apparatus - respectively the functionally connected devices on a subscriber connection - over a radio connection belonging to a telephone connection box for transmitting calls over the public telephone network, where both the telephone apparatus and the telephone connection box are provided. immediately connected to the telephone network, there is a transmitter and a receiver where the transmitter-receivers exchange device fixed and of the selected connection number for a telephone subscriber independent code-10 signals, and where a connection of the connection from the telephone apparatus to the public telephone network is only effected by established code. line.

Within the communication technology, various systems for communicating conversations between two interlocutors are known.

15 Telephone networks per Wire is widespread worldwide. Calls per Thread applies as particularly eavesdropping. Wireless stations are also used between stations whose position can be changed. With a wireless transmission it is possible to intercept without great risk to the interceptor. Car telephone systems perform the transmission on the line 20 between the vehicle and a telephone exchange by radiophony, and in the telephone exchange which can contact all mobile subscribers, the transmission to the telephone network takes place.

The present invention is based on the former transmission system. In the case of a conventional telephone connection, the transmission line on the network side leads to a telephone connection box which is connected to a telephone apparatus by means of a multi-conductor cable. The arrangement or arrangement of the telephone set is flexible within certain limits. In the first place, these limits are determined by the length of the cable. Alternatively, several device sockets have also been provided so that the range of operation of the telephone apparatus can be expanded.

However, for systems that are connected to the network, it was not possible for a long time to freely choose the location of the telephone device completely independent of the criteria "cable length and socket position". The most modern development step of the telephone system 35 which is tied to the network is in the view that the transmission line in the subscriber area, ie between the telephone connection box and the telephone apparatus, is wireless.

Thus, the telephone within a home, office or house can be included anywhere, wherever you stay for some time to receive calls and make calls yourself. Known plants 2

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of this kind, presupposes that sufficient frequencies are available to be able to assign each subscriber a separate frequency (private frequency). However, this condition cannot be fulfilled in practice, as only a small number of voice channels are released for this purpose by the postal administrations. The system would already be depleted in a very short time, while also ensuring, at low transmit power, that approximately twice the allocation of a frequency is not achieved within a range of 3 km. For example, when only 40 voice channels are available, it becomes clear that 10 such a system would have no chances in urban areas. It would be unavoidable for a call to reach more subscribers, and these could listen with a conversation. For the purposes of telecommunication secrecy, postal administrations do not allow such systems.

A system of this kind is described in U.S. Pat.

3476882. Assigned fixed frequencies are used here and in the case of denti fi cation codes.

In this connection, in the publication IEEE Vehicular Technology Conference from March 27-30, 1979, pages 20 159-162, New York, USA, a description of K. Yamada et al, entitled "2 GHz Band Cordless Telephone System," has been disclosed. ". Also in this publication, reference is made to the problem of the small available channel number. When reducing the transmit power, an influence is only possible to a small extent. The use of an identification signal 25 is suggested at too large a range of the carrier signal. The identification signal is transmitted from a telephone set to the connection box together with a fork switching signal and in the opposite direction together with the ring signal. By means of identification signals, incorrect connections must be avoided. Additional information, e.g. about 30 the special structure of individual stations does not appear in this publication.

For example, car telephone systems pursue another purpose. These facilities have one or more fixed stations, each of which is assigned a large number of mobile stations in automobiles. In these facilities, 35 had to solve the task of transferring a call that is received per call. wired at a fixed station corresponding to the "address" placed before the call to the correct mobile receiver among the many subscribers that can be selected. In the fixed station it will be per. wire incoming address within the framework of the many associated mobile stations, such as the 3

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fixed station can be connected to, translated into a code corresponding to the special address. All mobile stations receive the code and compare it with the station-fixed code. Only one mobile station, which recognizes the code as its own, cuts through the connection.

For example, apparatus of this kind is described in U.S. Patent No. 3,173,996 and in GB Patent No. 850,698. The mobile stations are equipped with transmitter search circuit to find a free work channel if needed. The fixed station is always informed of the channel occupancy and switches immediately to a vacant channel upon a call.

The known installations of the latter type relate to a wireless selection system. The fixed station can establish connections with a very large number of mobile stations. On the basis of the incoming call and its address, the code for selecting the recipient is determined.

In the systems of the invention, the subscriber connection box together with the cordless telephone set forms a functionally inseparable pair. The connection box can only be connected to the corresponding telephone set. Possibly 20 additional devices can be arranged side by side, but they all have the same nickname. A subscriber option does not exist within this transmission line. It was already taken at the exchange before the call's arrival at the junction box.

The object of the present invention is to avoid double seizure of one of the existing channels and to exclude an outgoing call over a neighboring connection box with the associated fee counter as well as to guarantee the interception security. This is achieved according to the invention in that, in both the wireless telephone apparatus and the connection box, there is a transmitter search path device for detecting a free channel or a free channel pair out of a number of predetermined transmission channels or transmission channel pairs at different frequencies, one apparatus from which the connection structure originates is stopped by finding a free channel or a free channel pair, and in that channel the code stored in a coding device in the transmitter in one device transmits the transmitter search process in the other device upon finding of a recorded channel or a pair of channel pairs is stopped when the transmitted code matches the code stored in a comparator coupler in the receiver of the other apparatus, 4

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and that there is a circuit for routing the wireless connection by code compliance in the comparator connection, in particular by duplex operation between telephone apparatus and telephone connection box or public telephone network. In this circuit design, it is prevented that each telephone set, together with its associated telephone connection box, must be assigned a fixed transmit and receive frequency.

If a call is to be transmitted wirelessly to the telephone set, the transmitter -in the associated telephone connection box, receives one of the associated scanning receiver as a free detected channel and sends out a code. The receiver in the telephone set constantly works with transmitter scan (scan operation), sequentially detects each recorded channel and ascertains whether its own code (eg 15 bit code) is connected. If this is the case, there is a shake hands to the connection box, the wireless 15 dupiex connection watching the channel is routed to the telephone network and the call is routed to the telephone set.

Conversely, if a call is to be conducted from the cordless telephone apparatus, one of the telephone apparatus's own scanning receiver as a free detected channel is recorded by the transmitter of the telephone apparatus 20 and the code is sent. The recipient in the telephone connection box, in contrast to the prior art, also works continuously with transmitter search (scan operation). It establishes, over the comparator coupling, compliance with the permanently stored code on which a receipt to the telephone set and connection to the telephone network is made. The transmitter power is sufficient to cover a range of e.g. 50 meters. Overlaps with neighboring systems cannot lead to errors, as the encoding of a channel detected as free by a 15-bit code allows at least 30,000 overlaps within the already limited transmission range.

The connection box according to the invention is thus comparatively comparable to a relay without its own intelligence, whereas a fixed station in the prior art can be compared with a central. The "fixed station" according to the invention (= connection box) forms the housing connection, which is assigned only a single connected call number. Thus, as in the prior art, the pair according to the invention, namely the connection box and the associated telephone apparatus, are individually wirelessly connected together over a selection process in the connection box. Due to the transmitter-fixed code, it is forcibly linked together in the connection box 5

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as in the telephone.

In the prior art radio network, only the subscriber station in question must be equipped with a transmitter search course device. The prior art must be able to connect to all subscriber stations by the prior art and therefore have as many transmitter receivers as it provides radio channels. In the system according to the invention, both the telephone apparatus and the telephone connection box have a transmitter search course device. In the radio networks, a free radio channel is searched by a subscriber in a local radio area, which is common to all subscribers. The problem of a division into a large number of radio ranges, whereby interfering with other radio ranges could cause a disruptive influence, such as a fault for division, is not affected by the prior art with regard to the radio network.

15 An increase in security can be achieved by the telephone to the receiver of the terminal box and the receiver of the telephone apparatus on the one hand and the receiver of the telephone apparatus and the receiver of the telephone terminal box on the other hand to have paired code, but different code from pair to pair.

The invention will then be explained in more detail with reference to the drawing, which shows a principle diagram of an embodiment of the device according to the invention.

25 30 35 6

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For example, between a wireless telephone set 1 and a telephone connection box 2, 4o transmission channels are available. The telephone apparatus 1 has a receiver 5 with transmitter search sequence and a transmitter 4. In the receiver 3, the transmission channels are constantly scanned (possibly in predetermined time intervals). A distinction is made between available and busy channels. The information on available channels is on the output 5 of the receiver 3. 10 When a keyboard 6 is operated, the transmitter 4 and the receiver 3 are connected to a free channel pair. First, the transmitter 4 on the free channel outputs a code supplied by a coding device 7 which constitutes the identification signal.

In the telephone connection box 2, there is also 15 a receiver 13 with transmitter search operations. This detects all recorded channels (output 18). In a connected comparator coupling 19, it is ascertained whether the transmitted code matches the code of the coding device 17 in the receiver 13. If the code is detected as correct, a "shake hands" from the terminal box 2 to the telephone apparatus 1 is detected.

The connection is then established and connected to the telephone network 2o. Above the keypad selector 6, a subscriber is selected and the call is routed 25 from the cordless telephone. The choice in no way affects the wireless connection and the code.

Conversely, if a call from the telephone network enters the telephone connection box 2, the information is first transmitted over one of the receiver 13 as a free detected 30 channel over the output 15 to the transmitter 14. The transmitter 14 sends the fixed transmitter code stored by the coding circuit 17.

The receiving station 3 continuously operating in the transmitter search sequence in the telephone set 1 sequentially transmits all signals on the recorded channels to the output 8, to which 35 a comparator connection 9 is connected. By comparison with the code on the receiver side from the code circuit 7, the connection request received over the transmitter 14 identified respectively found among the sum of those on different channels 7

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laughs incoming signals. The transmitter 4 then sends out its code which can match the transmitted code. The opposite receiver 13 receives the code and compares it with the stored code on the receiver side. It states conformity. Thus, the "shake hands" have been made, the loop to the switchboard is closed, and the call is routed over the wireless connection. The transmitter 14 and the receiver 3 as well as the transmitter 4 and the receiver 13 work in pairs with their fixed code. Both pairs can treat lo the same code or also be coded in pairs only. The key is that the code is invariable, from which the functional unit of connection box and telephone is obtained.

If signals from neighboring systems are intercepted by receivers 15 3 and 13, there is no danger that they will be passed on to the receiver as the readout is done by encoding, identification and acknowledgment. The telephone secret thus remains.

Conversely, it is also not possible from a telephone app-2o ready to enter a foreign telephone connection box and conduct a conversation over its fee counter.

For full duplex operation, 4o channel pairs are available.

The above is valid. With a receiving channel that is found free or recorded by receivers 3 or 13.

25, a transmitting channel is always connected. The system operates in the 9oo MHz band and the channel pairs frequency range is 45 MHz. The transmit power of lo mW is sufficient for distances between the telephone set 1 and the telephone connection box 2 until approx. 5o m. It allows you to manage with 4o channels.

3o In order that the individual channels in the telephone set 1 and the telephone connection box 2 do not have to be supplied with their own individual quartz, the frequency generation according to the synthesizer principle can be carried out by means of Phase-Locked-Loop (PLL). A freely oscillating oscillator (VCO) signal is thereby compared in a phase comparison coupling with a quartz-stable reference signal. The rising DC correction signal serves to re-regulate the VCO frequency to the desired frequency and simultaneously to channel selection.

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8 'channel channel relay. For this purpose, the VCO signal (f = 7o MHz) is first mixed at a frequency of approx.

1 MHz and then by means of a programmable divider divided by the step frequency. By switching the divider ratio, each channel frequency can be set. In order to realize the automatic search process, the variable parts must therefore only be programmed by means of a logical sequence control.

The stabilized VCO signal is applied partly to the receiver multiplier and partly to the transmitter mixer over each of the lo buffer amplifiers. The output of the receiver multiplier (approx. 85o MHz) is relieved of the unwanted spectral parts by means of a multi-pole wiring filter and fed to the first receiver mixer.

The control transmitter is quartz stabilized and operates 15 at a frequency of approx. 8o MHz. In a phase modulator, the oscillator signal is supplied with the information processed in the modulation amplifier.

Then, the modulated signal in the transmitter mixer is mixed with the VCO signal, the sum frequency is filtered out, and in the transmitter multiplier (x 6) is brought up to the transmitter's nominal frequency (about 9oo MHz). After amplification in the final stage, + 1o dBm transmit power is available.

Both on the antenna output and after the transmitter multiplier, a band filter is necessary to suppress undesirable frequencies as well as possible. Due to the high operating frequency, only so-called "Helix filters" are considered, since the required circuit goodness, together with small dimensions and poor throughput and high selectivity, can only be achieved with this kind of filters. A disadvantage here is the high fine-mechanical cost of producing such filters, but on the other hand, an optimum of interference safety (harmonic, mirror frequencies) is ensured.

The receiver works according to the double overlay principle. For single conversion, the intermediate frequency should be selected very high (1o-15o MHz) to avoid mirror-frequency interference as far as possible. However, the amplification and demodulation of high intermediate frequencies encounter difficulties

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9 (stability, poorer electrical efficiency).

The first intermediate frequency was set at 75 MHz, the second at 1o, 7 MHz. The receiver is, as far as possible, made according to a highly integrated design method.

5 After preselection in a 2-circuit band filter, level one of the utility signal is raised in the preamplifier and passed to the first mixer over an additional band filter. The second mixer converts the 75 MHz signal to 1o, 7 MHz and this is amplified, limited, demodulated and limited to the low frequency amplifier in the limiter amplifier.

The receiver also contains a noise barrier whose response threshold is adjustable. This ensures that a connection is made only when the signal-to-noise ratio (SNR) exceeds a certain minimum value. If a connection already exists, the connection is maintained for a few seconds after the minimum signal to noise ratio is maintained. If the signal-to-noise ratio does not rise above the minimum value during this time, the for-2o binding requirement is interrupted.

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Claims (2)

1. Wireless telephone equipment and stationary exclusively for the telephone system or the functionally connected devices of 5 a subscriber connection, over a radio connection belonging to a telephone connection box for transmitting calls over the public telephone network, where both in the telephone apparatus and in the telephone connection box connected directly to the telephone network , there is a transmitter and a receiver, where the transmitter-receivers exchange device fixed 10 and of the selected connection number for a telephone subscriber is independent code signal, and where a connection of the connection from the telephone apparatus to the public telephone network is effected only by established code compliance, characterized in that both in the wireless telephone apparatus (1) and in the connection box (2) 15 there is a transmitter search path device for detecting a free channel or channel pair out of a number of predetermined transmission channels or transmission channel pairs of different frequencies, a The transmitter search process in the one apparatus (1 or 2) from which the connection structure is based is stopped by finding a free 20 channel or a free channel pair, and in this channel it is transmitted in a coding device (7,17) in the transmitter (4 14) stored in one device (1 or 2) code that the transmitter search sequence in the other device (2 or 1) when a recorded channel or channel is paired is stopped when the transmitted code matches that of the transmitted code. comparator coupling (9,19) in the receiver (3.13) stored in the second apparatus (2 or 1), and a circuit for routing the wireless connection by code matching in the comparator coupling (9,19), in particular in duplex operation between telephone apparatus (1) and telephone connection box (2) or public telephone network (20). Wireless telephone set according to claim 1, characterized in that the transmitter (14) in the telephone connection box (2) and the receiver (3) in the telephone set (1) on one side and the transmitter (4) in the telephone set (1) and the receiver (13) in the telephone connection box (2), on the other hand, has pair-matching code, but different code from pair to pair.