2 ~ 3 ~ ~ . 7 METHOD FOR IN-HOUSE vOIcE_AND DATA l2l____ICATION THROUGH
THE IN-HOUSE POWER SUPPLY
~ he invention relates to a method and to a device for in-house voice and data communication, i. e.
transmission of voice and data signals, between communication terminals, in particular telephone-like devices, using at least two transmission channels, the in-house power supply lines being used as carrier for the transmission of information. Such communication systems with signalling of dialling forming in connection with a known private telephone system a small extension system ; without dedicated lines are known in the art from DE 37 07 310 C2 and DE 37 07 308 C2.
The communication systems described in the prior art referenced above comprise one central adapter unit and one or more exterior adapter units coupled to power supply lines. The central adapter unit also provides for ;~20 communication between the external public telephone network and the in-house communication network through a postal ~;~line transmission unit. To one exterior adapter unit is connected a respective normal extension phone set. In the exterior adapter unit, a hook switch splits the connection ~;~25 line in one carrier-frequency transmitting and receiving channel each having an adequate arrangement in the central adapter unit. Transmission of voice is effected by frequency modulation of the carrier frequency of the respective transmitting channel. Signalling of dialling is ef~ected over pilot-tone transmitters and receivers by means of selector relays, such that the establishment of a connection of one extension terminal with another one will take place over the central adapter unit.
A principle object of the invention is to provide a method allowing transmission of voice and data on the in-. .
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2~3~ .i 7 house power supply lines with small expenditure, and to allow a direct connection of a user with another one of a possibly large number of users on the in~house network, `~ without a central exchange or a bus master being required.
~- 5 The method of the invention is characterised as a method for in-house voice and data communication through the in-house power supply, using at least two transmission channels, voice communication being effected by means of frequency modulation, wherein data communication between the communication terminals, in particular the information for the structure of the connections, is performed in digital form by means of pulse modulation, and data communication between the communication terminals through ; 15 the in-house power supply operating as a bus consisting of two channels is effected by a handshake procedure.
one transmission channel is assigned to the calling party, and a second transmission channel is ; 20 assigned to the called party. The transmission channels have respective frequencies of 109 kilohertz and 131 kilohertz, with a maximum frequency variation of ~F = 3.5 ~ kilohertz, and are assigned to the called user and the ~~ calling user respectively.
~ 25 :.., According to one aspect of the invention, digital ~ telegrams are generated by switching the carrier frequency -`, !, on and off, and the set of a telegram consists of four blocks with block lengths L1, L2, ~ and L4, such that in the first block a "start of telegram" identification is transmitted, and the three remaining blocks, the sequence of which is arbitrary but predetermined, contain the ~i information "type of telegram", "source of telegram" and 1 "destination of telegram", and, if necessary, a header ~ 35 block of length Lo is transmitted prior to the telegram. -20~ 4j 'i The cora of the invention consists in a method for in-house voice and data communication between communication terminals, in particular telephone-like devices, using the in-house power supply. communication is effected between terminals through at least two transmission channels and no ;~ central exchange, e.g. in the form of a central adapter installation is required. When limited to two transmission channels, the in-house power supply is adapted as a bus with two carrier-frequency channels. The method according to the invention provides that exchange of data is achieved in digital form by pulse modulation of the carrier, and - that transmission of voice is effected by frequency modulation. The digital data exchange, in particular for dial set-up of a connection, is performed by means of data telegrams. When dialling, a hand-shake method is applied, ^~ i.e. upon receiving a "call telegram" of a call the called device will respond by an "acknowledgement telegram". For carrying-out the method, a transmitting and a receiving channel are assigned to the calling and the called parties ~ 20 respectively following a predetermined scheme. This scheme `~I of assignment may consist, e.g. in that the calling party , has always the channel having higher frequency as ; transmitting channel, and the channel having lower ` frequency as receiving channel.
The telegrams have a definite structure. Thus, e.g., a telegram comprises four blocks of block lengths L~, and L4 bits. The block lengths may be different or identical. The block transmitted first always contains a start of telegram identification, e.g. for a block length ~; 30 4 bits, the code 1010. Ths three remaining blocks contain information on the type of telegram, the source address and 'l~ the destination address of the telegram~ The type of telegram determines the type of action to be taken. Under 1~ certain circumstances, it is necessary to transmit, prior j 35 to transmitting the telegram, a leader block of defined ~ length, in order to activate other, inoperative, users.
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The method according to the invention is, thereforei, particularly advantageous in that data transmission in the form of telegrams with acknowledgement allows for a simple structure of the ~ommunication link between two users without central exchange. In inoperative condition, the users are on the power supply which serves as a data bus, and can accept either one, or both, talker as well as listener functions. The calling user accepts automatically the role of the bus master when initiating a call. Thus a central exchange or control station, i.e. a dedicated bus master is not required. The method allows for a great flexibility with regard of possible future applications by defining further activities in the in~ormation block type of telegram.
; The device of the invention is characterised as a i ~evice for in~house voice and data communication between communication terminals through the in-house power supply, ~ voice communication being effected by means of frequency r", 20 modulation of the carrier frequency of the transmitting channel, said device comprising a mains coupler with power supply unit; a transmitting channel; a receiving channel;
and a micro-controller with a network controller performing control of the device and establishment of a communication 25 connection with other communication terminals by exchange of digital telegrams with acknowledgement operation and transmitting the telegrams by means of pulse modulation.
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~`~ The device according to the invention, in the 30 following called a network telephone, contains a network coupler with integrated power supply unit, a receiver circuit, a transmitter circuit, a micro-controller and a ~; periphera} unit. It is particularly advantageous that each network telephone is provided with its own "intelligence", 35 because of the micro-controller. This micro-controller performs control of the complete network telephone, in ~4 ~ .
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particular the micro-controller controls communication with other communication devices, which may be, in particular, other network telephones. By transmitting digital telegrams comprising the information l~start o~ telegram identification", "type of telegram", "destination of telegram" and "source of telegram", a simple and direct structure of the connections is possible. There will also not be reguired a central exchange, as the called device knows, through the information "destination of telegram", - 10 that it is addressed, and through the information "type of telegram" the order to be performed. Through the information "source of telegram", it is possible to perform , an acknowledgement of the call.
;~ Another advantageous embodiment of the invention can be seen under the term "collision csnsiderations~. As long as the network is not occupied, all users have equal access to the network. If the network is occupied, and a device tries to establish a second connection, it will obtain the information "busy". Collisions can only then occur when two devices try to establish a connection with ~;`j a period of time of approximately 20 ms. In this case, there are two possibilities:
a) The called party cannot respond because of a mutilated telegram. Both callers obtain a "busy" signal.
25b) The called party recognizes the incoming telegram from the first caller and can transmit now an answering telegram. If he has recognized correctly the call address, a communication is established, and the second caller obtains a "busy" signal.
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If the called party has not recognized correctly the call address, case a) will apply. Collisions on the in-house network can, thus, be resolved safely.
35~ Another advantage of the invention is that the device offers great flexibility~with regard to possible . ~
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future applications by defining, e.g. further activities in the information block "type of telegram", or by extension of the telegrams by additional information blocks.
- The calling device occupies a transmitting channel and a receiving channel following an arbitrary, but predetermined scheme, which can be adapted such that the calling user occupies always the channel of higher ~10 frequency as transmitting channel, and the channel of lower :frequency ac receiving channel. This means that the called user automatically uses the lower frequency as a transmitting channel, and the higher frequency as a receiving channel. In an inoperative condition, all devices are listening, according to this scheme, on the higher frequency as receiving channel. The receiving and the transmitting channels of each device are, therefore, convertible with regard to frequency. The configuration scheme, once set-up together with the ~elegram system, 20 allows establishment of communication directly from one -device to another, without a central exchange with a pilot-r~tone dialling system being necessary.
In a simple way, an internal house communication system i8 achieved by using at least two devices according to the invention.
In the following, a preferred embodiment of the invention is described in more detail with reference to the appended drawings, wherein:
Figure 1 is a schematic block diagram of the network telephone of the invention;
Figure 2 is a schematic diagram of an in-house ~extension system on the in-house power supply; and : ~
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Figure 3 is a schematic diagram of a network interface for connection of the in-house telephone system to the external telephone system. -~
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Referring now to Figure 1, there is shown ~ block ; diagram of a network telephone being intended for in-house use through the in-house power supply. The network telephone comprises five functional groups: a mains coupler ~- 1, a receiving section 2, a transmitting section 3, a micro-controller 4, and a peripheral unit 5. The mains coupler 1 is separated from the remaining components accommodated in a hand set, and is connected to the hand set over a four-wire cable. The mains coupler 1 contains a power transformer 10 with a rectifier. Mains voltage is ,~ 15 transformed down to 15 volts ~low voltage), and is then transformed into a pulsating d.c. voltage. The latter is then reduced in the hand set to the required operational d.c. voltages of 12 volts and 5 volts, and is stabilized.
The pulsating d.c. voltage is supplied to the micro-; 20 controller 4 over the input 45, as it contains the information on the zero passage of the mains voltage. This zero passage information is used for synchronization purposes of the telegram transmission and reception. The mains coupler 1 can be connected by a protective plug to mains 13.
The receiving section 2 of the network telephone consists of a chain of three band filters 20, 22 and 24, to each of which are added amplifiers 21, 23 and 25, ~t;~ ~ respectively. ~he filtered and amplified f.m. signal is ~ed to a demodulator 26. From there, the voice signal transformed back to band base position passes to an ~fo : amplifier 27 and is supplied to a receiver cup 28. The demodulator 26 has a second output, through which the detected carrier frequency is fed to the input of the 35~ micro-controller 4. The band filters 20, 22 and 24 and the demodulator 26 are convertible by the micro-controller 4 J: ~
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;~ through the output 44 thereof in their centre frequencies ; between los kilohertz and 1~1 kilohertz. Further, the receive cup amplifier 27 can be switched on and off by the micro-controller 4 through the output 42 thereof. Thus, a voice signal is only connected to the receive cup 28 when the telegram exchange is terminated and the connection is established.
The transmitting section 3 contains, viewed in signal flow direction, a transmit cup 31 with a subsequent voice signal amplifier 32. The voice signal amplifier 32 has a transfer function with a pass band from 300 hertz to 3.4 kilohertz. The amplified and band-limited voice signal in base band position is transformed by a modulator 33 into a frequency-modulated signal. The modulator 33 generates ~;~ 15 a square-wave f.m. signal. This f.m. signal is fed to a , low-pass filter 34 and is then amplified in the transmitting amplifier 35. The low-pass filter 34 transforms the signal into a sinusoidal f.m. signal ~ containing no harmonics. The transmitting section 3 and `"~A 20 the receiving section 2 are combined in point 50 and are connected there with the mains coupler 1. The carrier frequency of the modulator 33 is adjusted by the micro-~ controller 4 through the output 47 thereof. Further, the ;~ transmitting amplifier 35 can be ~witched on and off by the micro-controller 4 through the output 46 thereof. ~hus, tl~ ~ the digital telegrams can be generated by the micro-controller 4 by switching the carrier frequency on and off.
The micro-controller 4 controls the complete -network~telephone and performs the following functions:
- switching transmitter and receiver on and off;
, ~ - executing channel assignment (conversion of transmitter~frequency and receiver filter to the respective channels);
- generating the dial signals;
~ reoognizing the own calling number, -. ~
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- generating the bell signal and the ringing and busy signals.
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Besides the inputs and outputs 42 to 47 of the micro-controller 4 described above, there is another input ; 41 for entries of the peripheral unit 5 to the micro-controller 4, and another output 48 for outputs of the micro-controller 4 to the peripheral unit 5.
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The peripheral unit 5 comprises a keyboard for generating the dialling information or other information, such as, for example, entry of a new own telephone number:
a hook contact for the information, whether the receiver has been lifted off or not; and a buzzer for generating the bell signal. In the present configuration with a block length of 4 bits for the telegram information "source of telegram", an arbitrary number from 1 to 9 can be entered ~ as telephone number of a network telephone. A maximum of : 9 users are thus possible in an in-house network. Larger numbers of users can be achieved by extending the block lengths of the telegram.
i, Referring now to Figure 2, there is shown the coupling between an internal house communication network through the power supply with the external public telephone ~; network. In the example shown, the internal house ;~ ~ communication network comprises the network telephones 65, 66 and 67 being connected with the in-house power supply.
As the network telephones can be connected to different pha~es of the house power network, the phases R, S and T
are bridged with respect to high frequency by a phase coupler 63. In order that conversations within a house cannot be tapped from outside, a carrier frequency blocking unit 64 is provided at the transition of the house network ..,~ .
to the external power distribution network. It is possible that house appliances, being connected to the in-house ~J~
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power supply as well, may generate a short-circuit to ground with respect to high freguencies of individual phases. Therefore, such house appliances must be provided with interference-suppressor filters 68, 69 and 70.
The transition from a house network to the public telephone network is accomplished by a network interface 62, which is connected to the in-house power supply, and to a cable terminal unit 60 comprising at least one master - 10 connection to the public telephone network. The cable terminal unit 60 comprises at least one hand set 61. With ~; such a configuration, an extension system is achieved.
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Figure 3 shows a diagrammatical block scheme of a 15 network interface. There is shown a network terminal 13 leading into the mains coupler l. At point 50 the receiving section 2 and the tran~mitting section 3 are connected to each other. The receiving and the J transmitting sections 3, 2 are acted upon by the micro-,, 20 controller 4 in the way as shown for the network telephones. For synchronization, the micro-controller 4 is supplied with the pulsing d.c. voltage from the mains coupler 1 through the input 45. The receiving section 2 and the transmitting section 3 lead into a hook circuit 80 25 being connected to an external adapter circuit 81 leading to an extension line 82. For transferring the dial information of the in-house communication method by means of transmission of information of the address in a digital telegram for an equal-rights user operation into the dial i~ 30 procedure of the public telephone network, the micro-!~ controller 4 controls a ralay driver 83 acting upon the external adapter circuit 81 and initiating there the 7~ required public dial procedure. For transferring the dial information from the public telephone network into the in-house communication network, the dial information is fed from the external adapter circuit 81 through the input 49 2~3~
to the micro-controller transforming such information into corresponding call telegrams.
; In another embodiment (not illustrated), voice transmission is effected in digital form. An A/D converter -is employed between the voice signal amplifier 32 and the modulator 33, and a D/A converter is located between the demodulator 26 and the amplifier 27. The modulated digital voice signal provided by the modulator 33 is generated by frequency conversion of the carrier frequency oscillation.
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