DE2546422C2 - Two-wire full duplex data transmission method and apparatus for carrying out the method - Google Patents

Description

description

The invention relates to a two-wire full duplex data transmission method according to the preamble of claim 1, as well as a device for execution this method according to the preamble of claim 2.

In the telephone industry, there are several types of connection systems in use that normally as exchanges for private business transactions (also called PBX), and the work with either analog or digital methods.

Such systems often use push-button type telephone sets. Speed dial is now closed different connected telephone lines possible. There are additional monitoring functions necessary, e.g. B. the displays BUSY, CALL and WAIT.

6G So that these additional oversight functions were possible, additional lines had to be used in addition to the actual voice transmission telephone lines be placed. This means that such a direct dial telephone can typically be connected to an entire cable bundle.

del from voice and monitoring lines connected to the PBX switching device. The more phone lines d. H. There were direct dialing lines, the larger the bundle of cables became. This type of part

I 3 4

α phone devices is under the designation 1 A2 pushbutton signals themselves through the special type of coding

S phones known can be done without difficulty, and it is on the

': In the case of frequent room changes, as is the case with normal, identical transmission paths, including transmission

£ take place in commercial buildings, it is necessary to use the signals sent by the remote stations

• 5 borrowed that the communication equipment from the 5 Ie possible, which is characterized by the coding frequencies of

fcä individuals are taken. Statistics, for example, show those sent by the local station

^! that, for example, in the USA and Canada divorce on average, and it is possible in the local station

Every IV ₂ years a room change of a certain one of these signals with the ones available there

Person takes place, so that the corresponding Ta signals to decode.

The trunk group assigned to the dialing telephone is also often OK. A device suitable for this method is

'I separated from the PBX switching device and is again based on the characteristic features of the

ί: 'must be connected. As a result, errors can occur.

j 5 proportional to the number of lines involved, the construction of this facility can be called in the tV, and the changeover requires switching means known to telecommunication transmission, such as Il substantial costs. 15 logical linking elements and D-flip-flops> ϊ With more modern systems, which can be set up according to the time multi-function without any difficulties. The entire U plux (TDM) method work, as it is in the circuit complexity is so low that it is easily described in han-% US-PS 36 00 518, 36 00 519 and 36 52 798 of the usual devices such as desk phones • i, a large number of push-button telephones must be accommodated. When moving a ψ remote device through a single device, usually in the form of a coaxial cable, the identification is required?! Connection line connected, and the voice recorder switching elements are included in the respective remote Gell binding such as the monitoring is carried out according to the time slot device, no change in the permanently installed ff allocation. This of course results in a large number of cables being required in the local station. In LEI | i complicated circuit of the individual Telefonappara- lead breakage or similar failures, only the loading ti tes, but the savings in copper wire laying, 25 striking apparatus is affected.
4, simpler means, and changing and moving the requirement that the delay in each case only advantageously, the I additional flexibility in these systems, as half of by the transfer rate (baud rate) be-B disadvantage of this system is to cause that during the waste period length, all of this one extension of the network between local and remote telephone sets is to be kept out of operation without further ado.
Become 0 '. ^{D 's} advantageous development according to claim 3 ER>? In a further telephone system, as it is possible, for example, in the event of a brief interruption of the,; As described in US-PS 36 37 939, each power supply will eliminate the possibly existing non-synchronous H push-button dial telephone connected by a telephone line run of the: 2-coaster stage and to 'i the one that contains only a single voice path, because norma - 35 synchronize. Thus, a further security of the rule on a telephone is only one call at the same time transmission for the monitoring data from which takes place. This single voice path is guaranteed by the local remote station

The station is switched so that it can identify the identity of any one of the following

assumes from a certain group of lines, explained in more detail with reference to the drawing; in this

determined by the buttons on the telephone set. 40 shows

; For the monitoring of the operating and activity to Fig. 1 a block diagram of a device suitable for the method would be connected to this push-button dial telephone, and

Connections is a four-wire monitoring line Fig. 2 (A) through 2 (Q) are a graphical representation of the on provided. Two wires are used to send monitoring information to the telephone set at various points in the circuit according to Rg.
As shown in Fig. 1, a local station and control information is to be received from the apparatus. a remote station with each other via a data-Also this is a noteworthy saving of line transmission line 10, which is designed as a twisted pair of line material, device and modification power and via a twisted pair of lines, but a separate 50 must be used for each connection serves as an analog voice transmission line 11, monitoring takes place. connected with each other. The invention is based on the object of designing a control station from a group of local stations of the type mentioned at the beginning, which, in conjunction with a switching device, are arranged with the least possible circuit complexity and device. Optionally, the local station can be located remotely from the switchgear with high savings in installation and modification and at a cost a safe and largely interference-free overhead can be connected to monitoring and feedback data by any suitable device, e.g. B. by a time division multiplex loop and a target. corresponding matching circuit.

This task is solved with a method according to In the remote telephone station the transmission ends

the claim !. 00 transmission line Ii for the (not shown) voice

In this way it is possible to run synchronously in a push-button telephone subscriber

de clock generator in all remote stations a clockco- rat 12. The subscriber set 12 has different

dated signal via the full duplex connection line, pushbuttons and light indicators (not shown),

gen to transmit, in the remote stations each connected to the monitoring circuit 13,

to decode and a return signal, which indicates the operating conditions. 65 In the local station, monitoring data

was the exact location of the respective remote station - applied to terminal 5 by the switching device

net, to trigger, the derivation of the decoding to the terminal 3 clock pulses are applied and a as

ren required auxiliary signals from the transmitted: 2-coaster acting flip-flop 4, which with the clock

Terminal 3 is connected, provides clock pulses with the The coded two-phase signal from the fork scarf ||

half repetition frequency at its outputs Q and Q. Device 24 is at the transmission line connection of the |

In the following, the circuit structure is received by the hybrid circuit 30 and in a known manner. <*? Description of the functional sequences of the output connection shown in FIG. 1. The coded two- φ. presented device, with reference to the in Fig. 2 5 phase signal passes through a low-pass filter 31 and 'illustrated waveforms explained in more detail. Each of the is by a pulse shaper circuit 32 into a; Switching elements called flip-flops have a rectangular shape and are provided with a DC voltage; ■■: data input D, a clock input CL and a complete component. The waveform of the signal at the ψ mental outputs Q and Q are based. In operation, the output of the pulse shaping circuit is similar to that in f ·, output Q assumes the state of input D when a positive pulse edge on the waveform at io Fig. 2 (G) and slightly delayed with respect to & input CL The output of the exclusive-OR element is located. The term "two-phase signal" is intended to be 23 in the following. The maximum permissible transmission delay is _; ί denote a coded signal, the average of which is less than half the period of the clock frequency. The co V ^ rather DC value in the middle between the entge- ied two-phase binary signal from the pulse shaping ty gengesetzten, extreme excursions of the Signalwel- 15 circuit 32 is connected to the negative (-) and positive (+) ~ \ lenform is the The term "two-phase binary signal" is intended to denote inputs of a non-retriggerable monostable, a two-phase signal, as is typically received from a digital circuit via a control circuit 33 which intervenes. The time constant of the multivibrator 34 is the DC supply voltage and the ground potential - more than half the period of the clock frequency, jetial works. Accordingly, the two-phase 20 takes less than the entire period. The signal at the out binary signal at any point in time one of two states of the multivibrator 34 corresponds to FIG. 2 (H). The ones that essentially correspond to the ground potential or the repetition frequency is the same as that of the clock that is essential to the DC supply voltage (FIG. 2 (A)), because they are due to the received surface. The two-phase signal is regenerated, it is equally

The (Fig. 2 (A)) applied to the clock pulse terminal 3 25 is delayed.

Clock pulses are divided by the flip-flop 4. The regenerated signal from the output of the monostable and appear at its output Q, as in the len multivibrator 34 is shown via an inverting connection Fig. 2 (B). The clock pulses of FIG. 2 (A) have stronger 35 at the CL input of a flip-flop 36 indicate a period of about 210 μS and those that apply. The encoded two-phase signal from the pulse fig. 2 (B) have a period of about 420 μS. Over- 30 iormer circuit 32 is also applied to the D input of the ί monitoring binary data, for example as in the flip-flop 36. The flip-flop 36 supplies at its <Fig. 2 (C) shown, the switching device is applied to (^ -output a partially decoded signal (Fig. 2 (K)). The input of a NAND gate 20. The Das Signal at this point has already partially decoded clock pulses at half the repetition frequency of FIG. 2 (B).

are to the other input of the NAND element 20 35 A flip-flop 38 supplies signals with half the clock frequency

applied and deliver a signal at its output, the quenz in phase with the section of low baud rate

corresponds to the illustration of Fig. 2 (D), which corresponds to the coded two-phase signal. The regenerated

the input D of a flip-flop 21 is applied The clock pulse signals from the output of the monostable

Clock pulses of Fig. 2 (A) are passed through an inverting circuit 34 to the CL input of the flip-flop

generating amplifier 22 inverted and connected to the input CL 40 38; in this flip-flop these signals

of the flip-flop 21 placed The resulting signal scaled down in order to deliver signals with half the clock frequency.

Schejnt at the output Q of the flip-flop 21 and corresponds to fern (Fig. 2 (J)). The output signal Q of the flip-flop 36

the signal shown in Fig. 2 (D), but it is related to the output signal of the inverting amplifier

inverted and linked to half the period of the clock pulse folker 35 via a NOR element 37 in order to

frequency, ie 105 microseconds, as in the 45 set signal to be supplied (Fig. 2 (M)). The reset signal

Fig. 2 (E) shown delayed. This signal is applied to the reset input R of the flip-flop 38.

NEN input of an exclusive OR element 23 applied; applies and causes the flip-flop 38 then to return

whose other input is the clock pulse that is applied when it is not in phase with the section

The result of the exclusive OR operation generates a lower baud rate or transmission speed.

encoded two-phase binary signal X (Fig. 2 (F)). From 50 speed of the coded two-phase signal should be how

a comparison of FIGS. 2 (C) and 2 (F) shows that this occurs when the power supply is interrupted.

the coded two-phase signal could occur at a baud rate.

The partially decoded signal from flip-flop 36 is g

is required to transfer the binary data bit rate to the input D of a flip-flop 39 where it

gen. Those sections of the signal that have the low 55 synchronous with the signals of half the clock frequency from the ^,

Represent portions of the binary data of Fig. 2 (C), ent flip-flop 38 applied to input CL , full;

speak the clock pulses of Fig. 2 (A) and have which is continuously decoded. This will make the binary data it

double the baud rate of those sections that deliver the ho at output Q of flip-flop 39 (Flg. 2 (L)):

hen sections of the data in Fig. 2 (C) represent for further use in the monitoring circuit:

and the signals with half the pulse repetition frequency 60 13. '

from the flip-flop 4 (Fig. 2 (B)). In addition to receiving continuous monitoring

The hybrid circuit 24 in the local station and transmission data generates the monitoring circuit 13

the hybrid circuit 30 in the remote telephone station also provides monitoring data for use in the assigned

are well known in the coded two-phase binary-ordered switching device. The generated monitoring

Signal from the output of the exclusive-OR element 23 is to 65 data are sent in binary form to input D.

The input terminal of hybrid circuit 24 is applied to a flip-flop 40 while regenerated

and consequently clock signals appear on the transmission line 10 at half the repetition frequency from the flip-flop 38

as a two-phase signal with no direct current component. (Fig. 2 (J)) attached to the input CL of the flip-flop 40 ϊ

are attached. The output signal (FIG. 2 (N)) resulting at the output Q of the flip-flop 40 is linked with an exclusive OR function with the regenerated clock signal of half the repetition frequency by an exclusive OR element 41 to form a two-phase binary signal with the lower baud rate (Rg. 2 (O)). This two-phase signal is transmitted to a pulse shaping circuit 52 via the hybrid circuit 30, the transmission line 10, the hybrid circuit 24 and a low-pass filter 51. Pulse shaping circuit 52 restores a DC level to the signal and converts the signal into a square wave form to provide a signal such as that of the pulse train shown in Fig. 2 (P) which is two-phase binary data Y. This signal is applied to the input D of a flip-flop 53 and decoded synchronously with the clock signals of half the repetition frequency applied to the input CL from the flip-flop 4 in order to supply the monitoring information (Rg. 2 (Q)) to the terminal 7.

The low-pass filters between the output terminals of the respective hybrid circuits and the pulse shaping circuits suppress voltage peaks caused by the steep edges of the input terminals applied signals and transmitted through the typical telephone hybrid circuit.

In the above description it has been shown that the device enables continuous two-way data transmission via a hybrid terminated two-wire transmission line will. In the local station, clock signals are used to generate a first transmission signal, that is used in the remote telephone station for both data and timing information will. Thus, the remote telephone station works delayed and synchronously with the clock signals in the local station. The signals received from the remote station are processed using the original Clock information is decoded in the local station in order to derive the returning monitoring data from it derive, provided that the synchronization of these signals in their forward and backward transmission less than is delayed by the full period of the original clock rate.

The requirement that the delay introduced by the transmission line be on the back and forth Return path is less than a certain value, sets a certain limit on the length of the in a certain System used transmission line. In a system with a maximum baud rate or transmission speed of, for example, 4.8 kbit / s, with the typical twisted pair of telephone lines with Copper conductors are used for indoor use, the maximum usable distance changes between the local station and the remote station primarily with the wire diameter or conductor diameter, as shown in the following table:

Wire diameter (mm)

Usable Distance (m)

0.4

0.51

0.64

1370 1610 1920

used outdoors, the usable distance is considerable enlarged. Of course, when the baud rate is reduced, the maximum usable distance is also used enlarged accordingly.

The hybrid circuits given in this example are normal speech path hybrid transmitters. Simple RC filters31 and 51 are used to avoid significant interference transmission through the fork transmitters

For this purpose 2 sheets of drawings

It has been shown that a reduction in capacity between the conductors, for example by using typical telephone lines to

Claims (2)

Claims 1. Two-wire full duplex data transmission method for control and monitoring data between a local station and a remote station, characterized in that, a) that a coded two-phase signal (Flg. 2 (F)) is formed and transmitted in the local station, which has first and second sections, which correspond to data bits to be transmitted in first and second states, respectively, the first sections having two Transitions per data bit and the second sections have four transitions per data bit, b) that from the encoded two-phase signal received in a remote station a first signal (Fig. 2 (H)) with the baud rate of the encoded two-phase signal and synchronously to this a second signal (Rg. 2 (J)) with half the baud rate and in phase with the first sections of the two-phase signal are generated, c) that the received encoded two-phase signal is synchronous with the first and the second Signal is decoded in order to obtain the data bits from it, d) that in the remote station another two-phase signal that is in the opposite direction represents data bits to be transmitted at half the baud rate of the encoded two-phase signal and is transmitted synchronized with the second signal, e) that in the local station this two-phase signal by less than half the period the baud rate of the encoded two-phase signal is received with a delay, and f) that the time phase signal is synchronous with one in phase with the first sections Signal is decoded in order to obtain the data bits transmitted in the opposite direction. 2. Apparatus for carrying out the method according to claim 1, with hybrid circuits in the local and in the remote station, and mn a key telephone set with associated monitoring circuitry in the remote station, characterized by the following features: In the local station there is a clock input (3) and a: 2-scaling stage (4) for the basic clock frequency (Fig. 2 (A)) of the first section of the coded two-phase signal or the basic clock frequency (Fig. 2 (B)) the second portion of the encoded two-phase signal (Fig. 2 (F)) is provided, logic elements (20, 22, 23) and a memory element (21) clocked by the inverted basic clock frequency (Fig. 2 (A)) of the first Absdii'iiUcS are connected to the input of the hybrid circuit (24) of the local station,
At the output of the hybrid circuit (24) of the local station is a low-pass filter (51) and a pulse shaper circuit (52) with the basic clock frequency (Fig. 2 (B)) of the second section of the coded two-phase signal (Fig. 2 (F)) clocked decoding element (53) connected,
the local station is connected to the remote station via a two-wire data transmission line (10) and a two-wire voice transmission line (11), The control circuit (33) for a non-retriggerable monovibrator (34) is connected to the output of the hybrid circuit (30) in the remote station via a low-pass filter (31) and a pulse shaper circuit (32), the time constant of the monovibrator circuit ( 34) is greater than '/ ϊί but less than! // "if / is the basic clock frequency (Fig. 2 (A)) of the first section of the encoded two-phase signal (Fig. 2 (F)),
The data input (D) of a decoding circuit (36, 39) is also connected to the output of the pulse shaping circuit (32), the output signal of which is applied to the monitoring circuit (13) of the remote station, and of which a first component (36 ) is clocked with the help of the monostable multivibrator (34), one also through the monostable multivibrator circuit (34) clocked: 2 reduction stage (38) is provided, the output signal of which also includes the second component (39) of the decoding circuit (36,39) clocks, and the monitoring data output signal of the monitoring circuit (13) of the remote station is applied to a logic element (41) via a memory element (40), and the output signal of the logic element (41) is applied to the input of the hybrid circuit (30) of the remote station, wherein the memory element (40) and the logic element (41) are both clocked with the frequency generated by the: 2 reduction stage (38).
3. Apparatus according to claim 2, characterized in that the inverted output signal (Fig. 2 (H)) of the monostable multivibrator (34) and the output signal (Fig. 2 (M)) of the first component (36) of the decoding circuit in of the remote station via a NOR element (37) to the reset input of the: 2 reduction stage (38).