FR2478915A1 - TERMINAL SUBSCRIBER EQUIPMENT FOR DIGITAL SWITCHING SYSTEM - Google Patents

Abstract

SUBSCRIBER TERMINAL EQUIPMENT FOR LOCAL DIGITAL TELEPHONE TRANSMISSION AND DATA NETWORK. THE POWER NECESSARY FOR THE CONVENTIONAL POWER SUPPLY OF THE TERMINAL EQUIPMENT 1A BY THE TELEPHONE CENTER, VIA THE TWO-WIRE SUBSCRIBER LINE 11, IS LIMITED BY DISCONNECTING CERTAIN UNITS FROM THE EQUIPMENT WHILE THE RINGER GENERATOR 31 IS OPERATING. THESE UNITS, ESPECIALLY THE DIGITAL SIGNAL TRANSMITTER 203, THE CODEC 35 AND THE SPEECH NETWORK 20, ARE POWERED ONLY AFTER THE HANDSET AND THE EQUIPMENT SYNCHRONIZED WITH THE CENTRAL. THE STALL SIGNAL G TRIGGERING THE BELL STOP VIA THE CONTROL CIRCUIT 199 AND THE SYN SYNCHRONIZATION SIGNAL EMITTED BY THE RECEIVER 197 CONSTITUTE FOR EXAMPLE THE ENTRY CONDITIONS FOR A DOOR AND 233 INCLUDING THE OUTPUT SIGNAL E CONTROL L POWER SUPPLY OF THE ABOVE UNITS 20, 35, 203.

Description

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  The present invention relates to a subscriber terminal equipment connected to a switching center of a digital communication system by a subscriber line and comprising a central processing unit, or processor, controlling the transmission of digital information signals on a subscriber line. the subscriber line, a ringing device, a dialing device, a hook switch, a speech network and a signal converter connected thereto for performing the analog-to-digital (AN) conversion of

speech signals.

  A digital communication system allowing the use of a subscriber terminal equipment of this type is described by German Offenlegungsschrift No. 27 58 109. More specifically, this patent relates to the transmission of different speech paths and data on a two-wire subscriber line connecting the subscriber terminal equipment and the associated line circuit in the center of

digital switching.

  If, in such a system, the subscriber terminal equipment is to be supplied from the switching center via a relatively long subscriber line, the transmitted electrical power may be too low to properly power all the electrical circuits. of

terminal equipment.

  The present invention therefore aims to provide a subscriber terminal equipment that can be powered from the switching center to which it is attached, even if it is very far from this

center.

  A subscriber terminal equipment according to the invention comprises for this a switching device which receives a first characteristic signal of the state of the switch hook on a first input, a second signal indicating the synchronization of the terminal equipment on a second input and that, when the hook switch indicates the stall of the handset and the terminal equipment is synchronized, provides an output signal controlling the connection of the units of the terminal equipment with their power source. Since the energy required to operate the striking device is quite high, the maximum consumption of the terminal equipment can be considerably reduced by disconnecting the units

  which are not needed during the ring phase.

  After the ringing device is disconnected when the handset is unhooked, all available energy can be used for

  transmission of speech signals.

  The invention will be better understood on reading the

  description which will follow, made as a non-limitative example, in

  referring to the appended figures which represent: FIG. 1, a diagram of the time-division multiplexed transmission channels of a communication system in which the subscriber terminal equipment according to the invention can be used; FIG. 2, the assignment of the bit time slots transmitted on the subscriber line to the individual transmission channels of FIG. 1; - Figure 3, the structure of the time division multiplex frame used in the communication system - Figure 4, a block diagram of the subscriber terminal equipment of the communication system to which the invention applies; FIG. 5, the terminal equipment of FIG. 4 with the individual lines of data and control; - Figure 6, a block diagram of the line circuit associated with the subscriber terminal equipment in a digital switch of the communication system; - Figure 7, the line circuit of Figure 6 with the individual lines of control data; FIG. 8 is a diagram of the additional equipment that can be connected to the terminal equipment for the transmission of data on two particular channels of FIGS. 1 and 2; Figure 9, the central unit and the converter of the terminal equipment of Figures 4 and 5; - Figure 10, the central unit of the line circuit of Figures 6 and 7; - Figure 11, a more detailed block diagram of

  the subscriber terminal equipment according to the invention.

  The present invention applies to a subscriber terminal equipment of a digital communication system, designated generally by the reference 1 in FIG. 1. This equipment 1 comprises a telephone set 2, in which the analog speech signals are set. in digital form by a suitable method - for example Pulse Code Modulation (PCM) - the resulting digital signals are then transferred to a HKA main transmission path. The signaling and timing information required for establishing and controlling a communication link is

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  transferred to a ZKS signaling and synchronization transmission channel. The terminal equipment may also be provided with a data terminal 3 of any type and which, as indicated by the presence of a switch 5, may be connected to the communication system. In this case, the digital data signals are transmitted on the main transmission channel IKA instead of the speech signals, while the signaling and synchronization information can be read from the ZKS channel or be

transferred to it.

  The terminal equipment may include an additional data terminal 7, which delivers digital data signals at a low bit rate. The bitstream (eb) is transferred to an additional transmission channel ZKD, while the signaling bits are transferred to the ZKS signaling path. Speech and data can only be transmitted on the HKA main transmission channel separately, but the additional data can be placed on the additional transmission channel simultaneously and independently of the transmission on the transmission channel.

main track.

  In the embodiment shown, the raw bit rate of the HKA main transmission channel is 64 Kbit / s, the ZKS signaling and synchronization channel and the data channel

  additional ZKD with the same raw bit rate of 8 K eb / S.

  The different eb trains are distributed over time by a time division multiplex circuit 9 and transmitted as a train at 80 K eb / s on a subscriber line 11 to a demultiplexer circuit 13 in the central, where the trains of eb of the main transmission channel HKA, the ZKS signaling and synchronization channel and the additional data channel ZKD are separated again. During data transmission in the opposite direction, that is to say from the central to the terminal equipment, the circuit 13 plays the role of multiplexer, while the circuit 9 plays that of demultiplexer, that is to say that he separates

eb trains.

  The subscriber line 11, and therefore the terminal equipment 1, is connected via a subscriber line circuit 15 to the corresponding central office (not shown), and through the central office to the rest of the network. telephone. The information and control signals are transmitted from the terminal equipment 1 on the main transmission channel HKA and the signaling and synchronization channel ZKS to the line circuit 15. The design of

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  The base of the latter is shown in FIG. 6. It may be provided with additional equipment 17 for connection to a data transmission network such as an integrated network, or a packet-switched network. The data exchange between the data terminal 7 and the additional equipment 17 takes place on the additional transmission channel ZKD, signaling and synchronization

on the tKS route.

  The additional equipment also serves to establish connections with the local videotex center. Communication with the videotex center may take place on the ZKD supplementary transmission channel while a long distance call is routed on the HKA main transmission path. Unlike the analog network

  classic local, a videotex call does not block the phone line.

  In addition, the capacity of the system is sufficient to ensure the transmission of signaling information for other services that will be

made thereafter.

  FIG. 2 shows an advantageous word structure of the digital signals transmitted on the subscriber line 11, that is to say the assignment of the successive eb's of the word to the different transmission channels. These eb, or more precisely the time intervals (IT) during which they are transmitted, are numbered from 1 to 10. The IT 1 to 8 of each word are assigned to the main transmission channel HKA, lIT 9 is assigned to the ZKS signaling and synchronization channel,

  and the IT 10 to the additional ZKD data transmission channel.

  The word duration is 125 microseconds, and the repetition frequency

words of 8 kHz.

  If the number of the bits within a word identifies the transmission paths, the frame structure shown in Figure 3 serves to define different words in the sequence of eb of each transmission path. A frame containing 32 words at 10 eb, the

frame length is 320 eb.

  At a repetition frequency of the 8 kHz word, it follows that the repetition frequency of the frame is 250 Hz, so that its

period is 4 ms.

  As shown in FIG. 3, V'IT 9 of words 1 to 8 of a frame is used for the synchronization of the frame, whereas V'IT 9

  words 9 to 32 of a frame are used for signaling.

  The signaling information formed from the aforementioned eb is used for the control of the network, that is to say the exchange of signals with the switching equipment and the exchange of information

  with special data services and additional services.

  Unlike the conventional local analog network, where states are generally signaled, in the communication system to which the invention applies, the events, i.e. the state changes, are signaled. The slgnalisation information is transmitted on the ZKS channel, outside the voice band. Audible tones are the only exception. A signaling word is divided into three sectors of 8 eb each (bytes): a header, a byte

  information, and a byte of control.

  The subscriber terminal equipment 1 (FIG. 4) comprises the telephone apparatus 2 with the following basic functions: a speech network with a receiver 21 and a transmitter 23, a switch hook 25, a numbering keypad 27 having 16 buttons, a 16-digit digital display 29, and a tone generator

of appeal 31.

  The speech network 20 (see FIG. 5) comprises a combination (not shown) equipped with a dynamic receiver 21 and a dynamic transmitter 23, and an adaptation circuit 33 which constitutes an interface with a converter 35. The circuit The purpose of the adaptation scheme 33 is to maintain the transmission values required by the telephone administration, such as reference equivalence, local effect reduction, frequency response, etc., and the level of handoff to the interface. The hook switch 25 signals the status of the subscriber station and triggers the synchronization phase in the digital line circuit

central office.

  The converter 35 comprises a CODEC (circuit - encoder -

  decoder), a filter, and a buffer. The band of the speech signal intercepted by the microphone 23 is limited by the low-pass filter, the speech signal is put in digital form and then code in words of 8 eb according to one of the recommendations of the CCITT. The coded words are taken in due time by a central station 37 located on the subscriber and transferred to the outgoing line of a serial data bus.

  39, which will be referred to in the following as "bus I 10 eb".

  In the sense of reception, the words of 8 eb are extracted from the transmission channel at 10 eb and then written in the buffer of the converter 35 under the control of a clock from the CPU 37. Here, the words MICs of 8 eb are used for continuous digital-to-analog (NA) conversion. The analog signal band is then limited to the voice band and the signal is applied to the

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  21. In the rest condition and in the condition of

  ring, the converter 35 is disconnected from the power supply.

  In addition to the functions mentioned above, when the handset is off hook, the hook switch disconnects the power of a call receiver circuit in the central unit 37 and at the same time connects the power of the speech network 20 and the converter 35, which includes the CODEC; when the handset is hung up, the speech network 20 and the converter 35 are not powered. 1 The dial pad 27 comprises, in addition to the usual buttons 1 to 10 for entering the call numbers directly into the central unit 37, a tax indicator button, another button for displaying the time and four additional buttons

  performing special functions.

  The digital display 29 is a 16-digit display having a suitable control circuit. The display is controlled by words

  coded signaling devices which are evaluated in the central unit 37.

  The display can for example indicate the time, the tax, the number

  composed by the calling subscriber or his calling number.

  The subscriber terminal equipment 1 comprises a coupling circuit (41) which differentiates the two directions of transmission and a power supply unit 43 provided with a stall detecting circuit. In the rest condition, the circuits of the terminal equipment are not powered, that is, the current does not flow. The power is switched by the stall detection circuit (a bit train detector). This circuit, which consumes very little energy in idle condition, applies the power supply when the telephone line is taken, this application being triggered: by the bit stream transmitted by the central office, or by the command the hook switch when lifting the handset, or - by commissioning additional equipment

  connected to the digital equipment.

  The central unit 37 located in the terminal equipment must perform the following tasks: synchronization of the terminal equipment 1, reception and transmission of signaling information, control of the converter 35 and more particularly of the CODEC which is there finds, finally orders additional equipment 37 which only

  the interface is shown in Figure 4 (see also Figure 8).

  German patent P 29 40 617 5 describes in detail the

  stall detection and the power supply unit 43.

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  The central unit 37, and the other circuits of the subscriber terminal equipment, including the telephone set 2, are interconnected by a data bus 39, control lines 47, pick-up and drop-out lines 49, and priority lines 51, which can be distinguished by their different representations

  graphs (see bottom of Figure 4).

  Call tone generator 31 operates in direct current. After the remotely controlled power unit 43 and its stall detecting circuit have been energized, the power of the call tone generator 31 is switched by means of a transmitted ringer control signal. through the transmission route of

  ZKS signaling and decoded in the central unit 37.

  The terminal equipment 1 is prepared for the modular extension.

  This is achieved by, among other things, designing the data path 39 as a serial transmission bus at 10 eb. The subscriber terminal equipment, at the location of the interface I formed by the data bus and the command and signal lines, can be added additional equipment 3.7 and an additional block or luxury equipment. 53, as already mentioned in the foregoing. Examples of luxury equipment are given by a full alphanumeric keyboard,

  an alphanumeric display and a special keyboard (not shown).

  Figure 5 shows the individual lines at the different interfaces, the units of the terminal equipment being designated by the same references as in Figure 4. Unlike the basic equipment, which is controlled from the central office, the additional equipment 3 , 7 and luxury equipment 53 are powered locally -by the 220 V sector. At the interface of additional equipment 3.7 and luxury equipment 53 are the following lines: socket (for signaling at from additional equipment), AK; release (for signaling from additional equipment), FR; binary clock, TB; frame clock, JR; word clock, TW; incoming data (in binary code), DE; outgoing data (in binary code)., DA; disconnection of CODEC, CA; and order

  starting or stopping power supply, STZ.

  At the interface II, in the case of a balanced two-wire line as shown in FIG. 5, the wires a and b of the subscriber line 11 are present. In the case of a four-wire balanced line, as can be used when the subscriber and the central are separated by a large distance, the interface is formed by the wires

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  c, d, e and f of the subscriber line 11.

  The interface III between the telephone set and the rest of the terminal equipment 1 comprises the following lines: analog input, AE; analog output, AA; start or stop control of the power supply (from the switch hook), STG; on / off for tone dialing R; a four-wire line DT for inputting data from the keyboard 27, a command line designated by the "sampling" reference from the keyboard 27, a four-wire data line DD, and a command line designated by

  the reference "sampling" directed to the digital display 29.

  The IV interface comprises the following lines: bit clock TB, system clock TS, clock words TW, incoming data encoded in binary DE, and outgoing data coded in binary DA. The V interface comprises the following lines: dissymmetrical connection line & on which are the data in line code; switching on or off of the power supply from the additional equipment, STZ and the central unit 37, STZ, start or stop command from the switch hook, STG. In the case of a four-wire line, this interface comprises instead of the line, an asymmetrical line i for the incoming data in line code, and an asymmetrical line 1 for the data.

outgoing in line code.

  The VI interface includes the following lines: CODEC in circuit, CE; reading (HIC words), L writing (HIC words), S; binary clock, TB; converter clock, (for example at 128 kHz), TK; and

clock of words, TW.

  We will now explain in detail the operation of the terminal equipment shown in Figures 4 and 5. The current required for the operation of the basic terminal equipment flows.

  between the wire a and the wire b of the subscriber line by means of a -

  coupling transformer included in the power supply unit 43, a constant operating voltage being regulated by a shunt regulator. As mentioned above, the power supply unit 43 includes a stall detecting circuit which detects a bit stream on the subscriber line 11. This stall detector is a receiver having a high input impedance and a response threshold. It consumes the small closed circuit current required from the coupling device whose load is zero in the present condition

  since the shunt regulator does not work.

  In the idle condition, no current flows in subscriber line II except for the small closed circuit current required for the stall detector. The power supply for all other units is off. It can be started either by the subscriber or by the additional equipment 3.7, or finally by the detector of

  bitstream (STG and STZ interface lines).

  The coupling transformer of the power supply unit 43 provides the necessary separation of potential and the adaptation of the level

  signal between the subscriber line II and the subscriber terminal equipment.

  Inside the terminal equipment 1 the transmission path is

  asymmetrical (interface line g of Figure 5).

  The terminal equipment 1 is protected against any overvoltages that may occur on the subscriber line 11 by a

  protective device in the power supply unit 43.

  The power supply unit of a 4-wire line differs from that described above in that the current is supplied by the wires c, d and e, f via two transformers. coupling and that the bit train detector controls the bitstream on the wires

e and d.

  The coupling circuit 41 which differentiates the two directions of transmission can be designed either for a two-wire line, in which case it operates in time or frequency multiplexing or in bidirectional mode simultaneous to a single frequency (duplex), or for a line four-wire, on which the two directions of transmission are

separated in space.

  The line coding is also performed in the coupling circuit 41. The incoming bit clock required for the line coding is derived by bit synchronization and is also usable by the CPU 37. The outgoing bit clock is provided by the unit

Central 37.

  In the case of a two-wire line the directions of transmission are separated by the following techniques. With respect to the V interface (FIG. 5), three types of transmission direction separation techniques must be distinguished: time multiplexing, single frequency duplex mode, or dual frequency duplex mode. In the first type, the signals are present in bursts, in the other two

  types, they are present in continuous form.

  The coupling circuit 41 is connected to the subscriber line 11 via the interface line g and the transformer

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  included in the power supply unit 43. In addition to the separation device itself, it includes coders and line decoders as well as control circuits and receivers with the equalizers

  and the required pulse shapers.

  The bit clock required in the terminal equipment 1 is derived in the coupling circuit 41 from the bit stream arriving on the subscriber line, and is transferred to the unit

  central 37 by the interface line TB.

  The incoming data extracted from the subscriber line II are packaged in the coupling circuit so as to be presented on the interface line DE in binary form, synchronously and in phase with the incoming bit clock TB. The system clock is also applied from the coupling unit 41 to the central unit 37. The clock of the outgoing words is applied in form

  continues to the central unit 37 via the line TW.

  In the terminal equipment 1 or in the additional equipment 3.7 the insertion of the outgoing data in the transmission channel at 10 eb is controlled by the central unit so that the data is presented on the interface line DA of way

  synchronous and in phase with the binary clock.

  If the communication takes place on a four-wire line, the coupling circuit 41 operates in spatial multiplexing. This differs from the coupling circuit of a two-wire line as far as

  a continuous data stream is present at the interface permanently.

  The CODEC and the filters in the converter 35, which perform the analog / digital and digital / analogue conversion of the speech signals, are connected to the transmitter and the receiver of the speech network 20 on the analog side and to the transmission path. eb on the digital side. The CPU 37 provides the clocks required for the operation of the CODEC and for writing and reading the PCM words of 8 eb in the data bus of 10 eb 39 or from it (FIG. 4): the binary clock TB, the clock of

  TK conversion and TW words clock.

  The converter 35 has control inputs CE (converter in "ON" position) and AC (converter in OFF position). The switching on and off of the converter is necessary to reduce the energy consumption in the condition " hung ", so that a sufficient amount of ringing current is usable, and during the transmission of data on the channel of

main transmission.

  In addition, the write and read pulses are produced for the CODEC of the converter 35. The PCM word of 8 eb is thus written in the data stream at 10 eb and read from it in due time. The interface line L is excited during the first eight periods of eb or 8 first ITs of each word of 10 eb which

  appears on the DE interface line.

  In the case of outgoing data, the MIC words of 8 eb are transferred into the outgoing data bus at 10 eb, i.e.

  DA interface line, in the first 8 ITs of each word.

  The write instruction from the CPU 37 marks the positions of the PCM words of 8 eb in the outgoing PCM transmission channel. The S interface line is excited during the first 8 ITs

  of each 10 eb word on the DA interface line.

  On the AB interface line, which extends to the matching circuit or interface device 33 of the speech network, the incoming signal is transmitted in analog form at a defined level. On the AA interface line, which comes from the interface device 33, the signal

  outgoing is also transmitted in analog form at a defined level.

  The digital - analog and analogue - digital conversion is carried out in the converter 35 according to law A of the CCITT G 711 notice. Transmission characteristics are in accordance with G 712

CCITT.

  The central unit 37 comprises a synchronization device for the derivation of the frame clock from the bit clock coming from the coupling circuit 41. In addition, it comprises a multiplexing control for the insertion of information into from the main transmission path HKA and the additional transmission channels ZKS, ZKD in the data bus at 10 eb and their extraction from the data bus. This provides the CODEC with the necessary write and read clocks and includes signal matching devices between the base equipment units - hook switch 25, dial pad 27, digital display 29 and tone generator. call 31 - and the additional transmission channel ZKS. The units 25, 27, 29 and 31 are connected to the central unit 37 via interface devices or adaptation circuits

61, 63, 65 and 67, respectively.

  If the terminal equipment 1 is provided with additional equipment, the bit clock, the word clock and the frame clock are supplied by the central unit 37 to the interface I of the additional equipment 3, 7 by intermediate lines TB, TW and TR respectively. The priority between the telephone set 2 and the additional equipment 3.7 is controlled by two other signals transferred on the FR and AR interface lines. In the outbound direction, the signaling information from the telephone takes precedence over that of the additional equipment, but in all cases a complete transmission is made from the additional equipment. The central unit 37 controls all the time sequences between the data bus 39 (interface IV), the converter 35 (interface VI), the signaling devices of the telephone set 2

  (interface III) and additional equipment 3 or 7 (interface I).

  In the central unit 37, a synchronization word of 8 eb is taken every ninth eb of the incoming data DE using the incoming data clock IB. The synchronization word is inserted into the outgoing data stream DA in the ninth ebb interval

  the first eight word periods of each frame (see Figure 3).

  During the stall phase, the synchronization is reinforced by the transfer of an eb configuration in the IT of the train

  outgoing binary that are not used for the synchronization word.

  The transfer is interrupted as soon as the stall signal has been detected. During the synchronization time, the incoming data stream, too, is provided with a synchronization configuration

  additional designed to speed up synchronization.

  It is considered that synchronization is performed when the synchronization word has been detected twice in succession. If the synchronization word has not been detected twice in a row, search for

synchronization continues.

  After the synchronization is completed, the CPU 37 provides the TB bit clock, the TR frame clock, and the TW word clock, which is derived from the frame clock. The binary clock is

issued in continuous form.

  The eb, word and frame periods start in mime

  time. A frame period has a length of 32 words and 320 eb.

  After the synchronization is completed, a continuous check is made to determine whether the code for a telephone call is contained in the header of a frame period of the incoming bit stream DE. If the stall signal is detected in the information sector at the same time as the header for the telephone communication, the transfer of the synchronization help eb configuration in the train will be interrupted first. outgoing data,

  then we will constantly check the condition of the switch hook.

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  Thus, from the quiescent condition, each change from the on-hook condition to the off-hook condition is transferred as a stall signal to the outgoing data stream, and each change from the unhooked condition to the outgoing data stream. "hang-up" condition is transferred in the outgoing data stream as a release signal, in the information sector of a period of

  frame, the header containing the code for the telephone communication.

  The seventh IT in the header contains the information sector identification tag: "O for control signal," 1 "for a symbol

  from a standardized international alphabet.

  To control the code of the converter 35, the central unit 37 produces either a read pulse L by which the CODEC is informed when a PCM word of 8 eb is present on the data bus 39, ie a write pulse S, by which the CODEC is informed of the moment when a word of 8 eb must be transferred on the bus of

data 39.

  To notify the subscriber of the arrival of a call, a memory is started at one of the inputs R of the calling device if the character "dial tone connection" is detected in the area of the call. informing a frame period of the incoming data stream DE at the same time as the header for the telephone communication. If the "call stop" character is detected in the same way, the memory

will be reset.

  The digital display 29 is controlled as follows. If the internationally normalized character in the information field of a frame period of the incoming bit stream DE is detected at the same time as the header of the telephone communication, the last four eb's are transferred in parallel on the command line DD to the display 29 together with a reading pulse

(sampling).

  The numbering is done as follows. If the central unit is selected by the buttons of the dialing device 27 via the four interface lines DT, the codes transmitted by the buttons and received by the central unit 37 are converted into corresponding characters coded in binary. The binary coded characters, as well as the character for "telephone communication" in the header, are transferred on the incoming data stream from the fourth to the seventh information sector IT of a frame period. The first three ITs of the information sector are assigned to the eb sequence

"110".

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  During signaling, parity checks are carried out with acknowledgments. If more stringent requirements are to be met, an error detection code character can be transferred into the control sector of each frame period of the outgoing bit stream. This code character is then checked and recognized at

the receiving end.

  At the interface l at the location of the additional equipment 3 or 7, the bit clock, the word clock and the frame clock are provided (lines TB, TW and TR), as it has been said above. above. To ensure that the signals are processed according to the priority, the interface line FR is no longer energized as soon as a pick-up or release signal from the switch hook 25 or a dial signal from the dialer 27 is to be transmitted on the data bus 39. The signal transmission is delayed until the interface line AK is excited by the additional equipment. This ensures that the transmission of any signal already

  initiated by the additional equipment will be completed.

  The interface line FR is also used to inform the respective additional equipment 3 or 7 of the condition of the subscriber terminal equipment. She can not be excited unless there is

  synchronism and if a catch signal has been received.

  The subscriber line circuit 15, shown in FIGS. 6 and 7 and also referred to as a "line circuit", is the link assigned to the subscriber between the subscriber's station. ie the subscriber terminal equipment 1, the subscriber line 11, the other central office equipment such as the control, the switching network, etc. (not shown in the figure) - and the additional service equipment 17. The individual units, which are similar in design and operation to the corresponding units of terminal equipment 1, are designated by corresponding reference characters to which a figure of 100 has been added, which is essentially a central unit. 137, a coupling circuit 141, and a power supply unit 143, which are interconnected by a serial data bus 139, control lines 147, stall and unhook lines 149 and priority lines 151 (see FIG.

Figure 6).

  The baseline circuit is designed to be connected to the central office and supplementary service equipment 17 through a very small number of connectors. This simplification is realized inter alia, by the use of the clock

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  central office as a reference or system clock, and

Serial data at 10 eb.

  The power supply unit 143 may be designed for a circuit to

  two wires (shown in the figure), or for a four-wire circuit.

  It comprises transformers for coupling the supply current to the subscriber line 11, the current being coupled to the wires a and b in the

  first case, and to the sons * c, d, e and f in the last case.

  Again, the power unit is provided with a pick-up circuit in the form of a bit train detector (in the case of four-wire operation only in the direction

  incoming), which responds when the subscriber line is taken (stall).

  The stall condition is indicated by a command line.

  The current coupled to the wires of the subscriber line 11 is maintained at a constant value given by a serial regulator. The bit stream detector, monitoring the state of the subscriber line 11 and connected in parallel with the transmission path is designed in the same manner as the bit train detector of the power unit 41 at the end. of transmission. It has a high input impedance receiver with a response threshold. A detected stall condition is indicated via a BK interface line

(Figure 7).

  The coupling transformer provides the necessary potential separation and signal level matching between the line circuit 15 and the subscriber line 11. Within the line circuit 15, the transmission path is asymmetrical (see FIG. . line

interface g of Figure 7).

  The line circuit 15 and all subsequent devices are protected against any overvoltages that may occur on the subscriber line II by protection devices in the unit

143.

  The power unit for a four-wire circuit differs from the circuit just described in that two coupling transformers are used to couple the current to the wires c, d and e, f, respectively, and that the bit train detector controls the train

binary on wires e and f.

  The coupling circuit 141 corresponds to that of the terminal equipment 1. It can be designed either for a two-wire circuit, in which case it comprises a coupling device operating in time-division multiplexing mode, in two-frequency duplex mode or in operating mode. duplex

  at a single frequency, ie for a four-wire circuit.

  * Zl 80'Z ap amaesss op a0olioq.p assalta UT B queuuoTiouo; Ot AX has AIX sevj.aeluT sa'i qe OT snq el south nuAnou ap enz; sje3s uoTxDuuo VI 4aeTvsuemgiddns aTtIaes opquemadTnba1l op AX agenjlu1il I la 'sesTmsuuai quos el3oe; u 3se Tnb uoTlisTIrUgts U-; e eludTDulad uoTssTmsuiza; p 0ToA eI salnes 'Ol lvauua al aaAe AIX azoBazuTt y * esTmsuvai; se qe 01 Q aToA pIl aueldnoz ap inTalO el DaAB çu IIX azieal; UTtI y' aSTQME ou eauuum aunfp gpuummoz TsuTu Isa saauuop ap xnt a'Ito uTusTltUts ap jom unp ale-uOl uOl uOl uOl uOl uOl uOIso uaIl uoI: oo ue: tp ue 9uTmeqae 3sa Sm1 'eluvalue uolzozalp UT suvp uoTeVST-Eu2ss op TOA V' * LI aTezuamglddns tSA. IBs op 3uemadTnbgT ú ai3o; u eDuueum.zad an Ise o alTiueam9lddns seauuop op uoTssTMSugjl apaToA el anb sioTe 'uolivinmmoD ap luemadnbbl ú a ea ;; g eouuuevmead a seelBdTvuTd uoTssTmsuali ap aToA in * -a3uuop ap snq np Tz-sellae op uoTlB> [ilxal inod no qa 01 Q saeuuop ap snq ael sup aalTvuamqiddns to aludtouTlad uoTssTmsuBlz ap GBUOA sap $ uollmzou; T sep uoTçiesuTT rnod aSeuxedTzlnm ap la-guz usTuolqaues and ap uo; ianip ep guo $ Eisuo.aqzuls ep suoTlvanmi; uoe sap uoTianpold Bp s; tjlTsodsTp sep eazodmoa aleiluae giTun, * (g9 aean2T;) IF apummo ap aU2IS eunip eaiTeTpm. eluT5l aed emalsis ep eaolioql and squemTe zuos the 0Oc zolq an aud ssnssnnnsssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssss quuoqui gi ael anb soe eallem apom ael suup auuoTizuot quuoqv1p anbTlamnu alonoq el ap Tealuae 91o ael ialzuea np agoTlioqI avcd aesTuoiqzuús inel snld Tp vil no ammoa Z9ul. 9l alalIuaM flun, * sodaez ap zul Lt easuqd ap uoTpesuadmoe aun anza; jea no aeSo-ioqT ap uope3oaae ;; l l uanent; uu ti ue ss uiTiegudoad ap sdmae ael anb aqJatduma, p uTyY * (L an2T;) allns el aeda aalaop eA noi anb aeT1aug.p aoanos aun Q, nbsn 3uoA Tnb ZOR qa A / e '1> aeeupaluuTp SauTtI sToil saTuano; Iuos uI aeao V * LY I aa $ Buamemlddns aTla.as ap quamadsnbal O0 ap no lealuaz np-aTlacd tiqltlIluamTllep qiunu, suvp eagqzoazgp apanealoap np aTaud I auemTe am3g Inad qa sodaez ap uoTiTpuo el suvp a3uemTIe south esaeu auSTI ap anapo ael anb au ua euamalnes quuoqe 3go T t ageldnov ap iTnoTo np ala; lp ll azTun'l -LET elriueD ç 2iTun, t Ied alqusTllTn luamale2a Isa the (eajzm agolioq aaladdu) lilxuae np aeolaoql ep a P aalap his ele anod aeTvsseDau azurilos alTeuTq e2oIloqq * au2tI ep eepoz el luemaleuS esTlega II * saneadeaza sap 3a auSTi ep sepuemmoD sap puaedmoD îlq eavldnoz Bp inzaTz el

SL68LZ3

17 - 2478915

  For the signaling in the outgoing direction the central unit 137 also controls the priority between the central i50 and the supplementary service equipment 17, always in favor of the telephone communication. The CPU 137 controls all time sequences between the data bus 139 (interface XIII), the central office (interface XIV) and the additional service equipment

(XV interface).

  The system clock, the word clock and the clock of

  frame can be used on the TS, TW and TR lines of the XIV interface.

  The bit clock (80 kHz) and all the write and read clocks required for multiplexing and time slot changes are derived from these clocks. Periods of eb, words and

weft start at the same time.

  The synchronization pattern is generated in the central by the transfer of the synchronization word in the ninth IT of the first eight word periods of each frame period of the outgoing data stream DA. In the opposite direction, the synchronization word returned by the subscriber terminal equipment 1 is extracted from

  every ninth eh of the incoming data stream DE.

  An eb configuration that enhances synchronization is transferred to the other outgoing data stream ITs, which are not used for the synchronization word. The transfer is interrupted as soon as synchronization is performed. During the stall phase, the incoming data stream DA also has an additional synchronization configuration. This configuration is evaluated and used to speed up synchronization. It is considered that synchronization has been performed if the synchronization word has been detected twice in succession. If the synchronization word is not

  detected twice in succession, we will have to start the synchronization again.

  After the detection of the synchronism, a catch signal, as well as the code of the "telephone communication" in the header of a signaling word, is transferred into the information sector of a signal.

  frame period of the outgoing data stream.

  The main transmission path on the interface line DE of the data bus 139 is assigned to the transmission path at 8 eb of the central office 150 on the interface line HE. Conversely, the 8 eb transmission path of the central office 150 on the HA interface line is permanently assigned to the main transmission path within the transmission path at 10 eb on the DA interface line. The logical state of the first eight eb's of each word period of the path of

18 2 4789 15

  transmission at 10 eb is transferred in the eight ITs of a corresponding word period of the data transmission path to 8 eb of

  additional service equipment, and vice versa.

  The central unit 137 includes the memories necessary for this transfer. If the code for the "telephone call" on the DE line interface is detected in the header of a frame period, the logical states of the 8 eb of the information sector are transferred in the ITs 2 to 9 of a corresponding frame period of the signaling channel on the interface line SE, the signaling condition (logic 1) being indicated by the first eb If the header for the "telephone communication" is is not detected, the logical states of the 16 eb of the header and the information sector are transferred in the ITs 2 to 17 of a corresponding frame period of the signal path.

  transmission of additional service equipment 17.

  In the outbound direction, the signaling path is used either by the central office 150 or by the service equipment

  additional 17, according to priority.

  If a logic state 1 is detected on the SA interface line in the first IT of a frame period, the states of the second to the ninth eb, as well as the code for the "telephone communication" in the header are transferred to the information sector of a frame period in the transmission path at 10 eb on the DA line interface, otherwise the states of the second through seventeenth eb of the transmission path on the line of transmission DA interface of the XV interface are

  transferred to the header of the information area.

  The additional transmission path on the DE interface line is permanently assigned to the transmission path of the

  Additional service equipment data at the XV interface.

  Conversely, the data transmission path of the supplementary service equipment on the line DA of the interface XV is permanently assigned to the additional transmission channel in the channel at 10 eh of the DA interface line. The logical state of the tenth eb of each word period of the transmission channel at 10 eb is transferred to the first IT of a corresponding frame period of the data channel.

  additional service equipment, and vice versa.

  During signaling in the transmission channel at 10 eb, parity checks with acknowledgments are carried out. If more stringent requirements are imposed with regard to the "protection of signals, it is possible to introduce an error detection code

19 24 789 15

  in the control sector of each frame period of the outgoing data stream. This code is then checked and recognized at the end

reception.

  As soon as a logic state 1 is detected in the first IT of a frame period on the line SA of the interface XIV, the line TR at the interface XV is no longer energized until the available signal was transferred to the transmission channel at 10 eb. If the AK interface line is active, the signal transmission will be delayed accordingly. This ensures that the transmission of a signal already initiated by the supplementary service equipment 17 will be completed. Line

  FR interface can be excited only in the synchronous condition.

  At the interface XV, in addition to the line TB for the bit clock, the lines TRE and TRS for the frame clock in the reception and transmission directions respectively and the lines TWE and TWS for the clock of the words in the directions of reception and

  transmission, respectively, are present.

  The subscriber terminal equipment is supplied with energy by a central constant current source 155, which can be connected or disconnected via lines BK, BGZ and A. The DC current supplied by this source is coupled to the subscriber line 11 in

the power unit 143.

  Figure 8 shows details of the additional equipment of the subscriber terminal equipment. There are two types of additional equipment: the additional equipment 3, 3A for the transmission of data on the main transmission channel, and the additional equipment 7, 7A for the transmission of data.

  on the additional transmission path (see also Figure 1).

* The additional equipment 3, 3A are mainly data transmission equipment with V or X interfaces according to CCITT specifications. On the contrary, the additional equipment 7, 7A can be of various types, for example videotex, c

teleprinter or telefax.

  The additional equipment 3, 3A, 7 and 7A are connected to the terminal equipment 1 via interface devices 157, 159, 161 and 163, respectively. As already mentioned above, the interface comprises data bus 39, control lines 47, lines 49 for connection and disconnection of the power supply.

  the terminal equipment 1, and the priority control lines 51.

  For signaling in the outgoing direction, the terminal equipment 1 has priority if there is more than one equipment szuemadTnbg sep aTlTTpgmaeluTl jad saauuop ap saoT & aals sap xd 01 VX aleedTzuTld uoTssTmsuual apaToA el op 8esTd Bl 3p siol * sIom sep agolioql ap alTuTq agolioqj ap sagATap qUOS ueD 7nod saiTssezqu ainlDae ap the ainilav, p his $ olaoq sl.qa 0I e saauuop ap snq nB sia.lxuemgiddns luamadTnbg, t ap sauuop ap uoTssTmsuel7 ap eTOA BI 5 ladvpB 12 squTlsep ('0i3 <s9arouîm ooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo TeluemgIddns sluemadTnbg seI suBp gsTlITn asTld ap oc jTzzedsea adX4 ne aleuuj uoTfludvpeT 4snîd ea Daa; .azuTp s; T.TsodsTp sap solBuiug seq sawvd sep: help t e lueaxdsuxal amio; aTquestliTn all.TuamgIddns uoTssTmsuva: op eToA T vI j Taedsai alTvluamgIddns IuamedTnbT ap saQuuop op uoTss9Tmsusil p eToA 8I ialdwpw mnod (-me <aal [Tomm <apon Qp sanass $ TiaAuoo) sTlgTsodsTp sep luamaI23, çz zueuuaidmou E91 '19! in; taezuT & p siTnDiTz salt * saTuano; juos sagTldoiddu suodmwe saalomqm sap 'l TeuTmaal uemadTnbIT ap aTxoTld UT xainssv t UOSe ap xnfutls Qp uotssTmsuel3l UTLTUOUSS TS *' uameaTo3dsai '6 1 LET 3tzluTP sTniT p lQ L LI SQDoop s; TiTsodsTp salt ouzaouoz Tnb av uae Tnpoid es asoqp amgm eu * saallTuTod oz sepHl Sep sepad yean $ tU and suvp s9nbTpuT 3Uos' is 6 'L4' 6u aDgelpUTp ssu ssu3u 3uQtQcsssLtLQcu1y 191 aejaelZuTp s5TzTsodsTp salt sWlnbsl sa5aiAB2 B ILI 691 8sTITo0dsTP salt * 10o sep esolloql ap qe gemvz ap eo0loq11 op 4aiTvuTq e2SoTioqTI p saeAhagp zuos 9soeuuop sep iesuei; do not know how to do this, and do not hesitate to do so. * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * and # 6UI snq et suep sequuo pp uoT: fnpoaIuTT anod sTuino0 zuos sITlTsodsp sap 0o Ssnld ea * aeleuuoD ise I IuTumea 3uemodTnbga suvp ú9 uoTsuemT-Iwsp giTunl gaiuviaos astlad ap seD and suea * -aauelos la eluvaue suolzoaTp salt surp snq np xnwuSTs op quemeAQtlgd op no qa 0O Q se3uuop ap SNQ el years uoTlligqTT op the OsTld p xneu2gTs op uolTonpoiluTp s; TltsodsTp September ellodmoD aiTviuemgtddns uoTssTmsuVaI op Etoa el s years saeuuop ap uoTssTmsuevl el 7nod G9L the 191 sDetjaleUT salt * 1ugmeATieedsai U91 No. 9g auSTIT ANd years a9puemmoz qse s; lTpadsea salîTeuamglddns siuemadTnbg set aiue giTlotld eT 4VL 'L no V' 4u eaTuluamgTddns

SL68ZZ

oz

21 2478 915

  3, the CODEC contained in the converter 35 of the terminal equipment 1 is disconnected from the power supply via the corresponding interface circuit. The equipment

  additional is released only if there is synchronism.

  The design of the CPU 37 and the converter 35 of the terminal equipment 1 appears in FIG. 9. The CPU 31 essentially comprises a transmitter 171, a control 173, a clock generator 175 and a receiver 177, which are interconnected by appropriate lines. The transmitter 171 comprises a transmission memory 179, a synchronization circuit 181, and a signal encoder 183. The receiver 177 comprises a reception memory 185,

  a synchronization circuit 187 and a signal decoder 189.

  The interface lines that connect the central unit to the other units of the terminal equipment 1 correspond to the interface lines of FIG. 5 as indicated in dotted lines interfaces I, III, IV and VI. At the interface VI between the central unit 37 and the converter 35, the lines L and S for the transmission of read and write pulses respectively, are combined in

a common LIS line.

  Via the interface I can be connected the central unit 37 to the additional equipment 3 and 7 and the additional block 53. Via the interface III, the central unit 37 is connected to the telephone set 2 , and via the interface IV, it is connected to the coupling circuit 41. A line designated by the reference 'aus' is used to disconnect the unit

43 power supply.

  The converter 35 comprises a speech band limiting filter 191, a codec 193 which performs the D / A and A / D conversion, and a memory 195, in which the incoming digitized speech signals and

  outbound are temporarily put in reserve.

  Fig. 10 illustrates the design of the central unit 137 of the subscriber line circuit 15 at the central office. It comprises a receiver 197, a control 199, a clock generator 201, and a transmitter 203 which are interconnected by appropriate lines. The receiver 197 comprises a reception memory 205, a transmission memory 207, a signal decoder 209, a synchronization circuit 211, and a

signal decoder 213.

  The transmitter 203 comprises a transmission memory 215, a reception memory 217, a signal coder 219, a signal circuit.

  synchronization 221, and a signal decoder 223.

22 2478915

  The interface lines that connect the CPU 137 to the other units of the line circuit 15 are the same as those in FIG. 7

  and have already been partially explained in the foregoing description.

  This is also indicated by the dotted line interfaces XIII, XIV and XV. Via the interface XIII, the central unit is connected to the coupling circuit 141. Via the interface XIV it is connected to the central 150 and, via the interface XV, it can be connected to the supplementary service equipment 17, which establishes the connection between the main transmission channel - in the case of data transmission - or the additional transmission channel and the different data networks, or for example, the videotex center. A line designated by

  the reference "aus" is used to disconnect the energy source 155.

  We will now explain the operation of the lines

  provided at interfaces XI and XV of FIGS. 7 and 10.

  The interface XI comprises the wires a and b of the balanced subscriber line11. In the case of a balanced four-wire line, the

son C, d, e. and f are present.

  At the interface XII, in the case of a two-wire circuit, there is provided an asymmetrical line g for the transmission in line code, in the case of a four-wire circuit, an asymmetrical line for the incoming data. in line code, and an unbalanced line for the outgoing data in line code. In addition, there is a line BK for the incoming plug, and a line for the current plug

constant.

  At interface XIII the following lines are present: 1S for the system clock, TB for the binary clock, TW for the word clock, DE for the binary coded incoming data, DA for the outgoing data coded in binary. The interface XIV comprises the following lines: TS, TW and TR for the system clock, the clock of the words and the frame clock respectively, SE for the incoming signaling information, SA for the outgoing signaling information, HE for the incoming main transmission path, HA for the main outgoing transmission path, and BGV for taking from the

central 150.

  At interface XV are provided the following lines: _4 for taking from supplementary service equipment 17, DA for outgoing data coded in binary, DE for incoming data coded in binary, FR for clearing (for signaling from additional service equipment), AK

24 78 9 15

  for excitation (for signaling from supplementary service equipment), TB for the bit clock, TWS for the word clock in the send direction, TBS for the bit clock in the receive direction, TWE for word clock in receive direction, TRS for frame clock, transmit direction, and TRE

  for the frame clock in the receiving direction.

  The CPU 37 and the CPU 137 are both designed as purely hardware circuits that can be

  built with active and passive components available in: &.

  trade and can be achieved advantageously by having

  use of integrated circuit techniques.

  The additional transmission channel ZKD (see Fig. 1) can be used either for the transmission of a data service (eg videotex, teletex, or telefax) at a certain time, while nevertheless being able to transmit different services at different times, either to establish connections for the different services at the same time, in which case a sub-frame is allocated to the individual services. In the signaling and synchronization-ZKS transmission channel, in addition to the signaling information for the main transmission channel HKA and the additional data transmission channel ZKD, signals can be exchanged between a subscriber

  and central equipment, such as an alarm center.

  The allocation of the information transmission channel may also be as follows: a 64 keb / s main transmission channel, a 2 keb / set synchronization transmission channel, an additional data transmission and transmission channel. signaling at 14 keb / s additional data and the signaling data being transmitted as information packets on a basis of equal priority and, if so

  necessary, for several services simultaneously.

  The division of the terminal equipment 1, and the line circuit 15 into several functional units and the clearly defined interfaces allow a modular construction of the communication system to which the invention applies. In particular, the system can be adapted to different coupling techniques by replacing the coupling circuit 41 or 141, which is arranged on a printed circuit board. The separation of the terminal equipment 1 from the luxury equipment 53, the additional equipment 3 for the transmission of data on the main transmission path, and the

24789 15

  additional equipment 7 for the transmission of data on the additional transmission channel, which can be connected via the interface 1 (FIGS. 5 and 6) using simple connectors, allows the basic telephone apparatus to be powered remotely via the central line. Inver.sement, additional amenities and luxury amenities are locally powered. For a transition period that will likely take some time, the desired all-digital telephone network will not be present yet, so that digital subscriber loops can be operated in conjunction with the local analog exchanges. In such cases, a suitable matching device can be inserted between the line circuit 15 and the analogue exchange which provides, among other things, a D / A conversion and

  A / N and a signaling adaptation.

  The subscriber terminal equipment IA according to the invention will now be described in more detail with reference to FIG. 11. It comprises at least the following devices: the speech network equipped with a microphone and an earpiece, the hook switch 25, the dial pad 27 and the ringing device 31 with tone generator call. It may also include an alphanumeric display device and other luxury accessories (not shown). The central processing unit 237, or signal processing processor required for establishing a telephone call and controlling the transmission of the digital speech sample signals on the subscriber line 11, comprises the receiver 197 which processes the incoming signals, the transmitter 203 which processes the outgoing signals and the control circuit 199, with clock generator 20 ', which controls the two

other devices.

  A line terminator 231 establishes the connection of the terminal equipment to the subscriber line 11. The termination 231 contains in particular a supply circuit which couples the power from the central office to the terminal equipment and adjusts the supply voltage at a constant level. The supply voltage is applied to the aforementioned units of the subscriber terminal equipment IA. Termination 231 may also include the separation circuit of the two

  transmission direction 41 of FIG. 4.

  The power of the buzzer signal generator 31 is switched from the central office by means of a signal word which is

2,478,915

  As all units of the terminal equipment 1A do not need to operate during the ring phase, they may be temporarily disconnected from the power source. The units thus disconnected are the signal converter 35 which contains a codec and the filters, and the transmitter 203 of the processor 237. The supply of these parts of the terminal equipment becomes necessary only when the called subscriber has taken off. and that the

  synchronism is reached between the central and the equipment lA.

  A switching device 233 which, in the embodiment

  presented, is an AND gate, has two connected inputs respectively

  The switch hook 25 provides an output signal G which is at logic level 1 when the handset is off-hook. The receiver 197 provides a logical level SYN signal 1 when the synchronization is

  obtained between the central of the subscriber terminal equipment lA. As a result

  When the two signals G and SYN of level I are applied to the switching device 233, the latter produces a start signal E which is transmitted to the converter 35 and to the transmitter 203 so that

to ensure food.

  If the circuits are made using CMOS technology, their power supply

  This is done by authorizing all their dynamic entries.

  In the static state, the consumption of CMOS integrated circuits is indeed extremely low, since most of the energy they use is determined by dynamic processes, in particular

  by charge transfer between capacitors. Therefore, switching

  The state of work at a state of rest with almost zero consumption can be obtained by prohibiting dynamic inputs. The prohibition or authorization signal for these entries may be transmitted by

simple logical doors.

  The ringing device consumes approximately 50 mW. The decency

  the converter 35 and the transmitter 203, or parts thereof

  units, saves 50 mW. In general, if the decrease in

  the disconnection of a sufficient quantity of units is equal to the power required for the bell, the total power

  must be provided to the terminal equipment IA during the phases of

  and conversation remains constant. This avoids any peaks of consumption corresponding to an energy impossible to transmit by the subscriber line when the latter is very long. An equipment

  The subscriber terminal according to the invention therefore increases the distances covered by

  by the telephone network or the power available for

  supply of subscriber equipment.

Claims (4)

  1 - Subscriber terminal equipment for digital communication system, said equipment being connected to a switching center of said system by a subscriber line and comprising a central control unit for the transmission of digital information signals on said line and a ringing device, a numbering device, a switch hook, a speech network, a signal converter coupled to said network for performing the analog to digital conversion (AN) of the speech signals and being characterized by the fact that it also comprises a switching device (233) which receives on one input a first signal (G) characteristic of the state of the switch hook (25) and, on another input, a second signal (SYN) indicating the synchronization of the terminal equipment (lA) with the switching center, and provides an output signal (E) allowing the supply of certain units of the terminal equipment when the two conditions of stalling the handset   telephone and synchronization are carried out.   2 - Subscriber terminal equipment according to claim 1, characterized in that the output signal (E) of the switching device (233) controls the power supply of the signal converter. (35).   3 - Subscriber terminal equipment according to claim 1 or 2, characterized in that the output signal (E) of the switching device (233) controls the power supply of a transmission device (203) contained in the central unit (237) and processing   the signals transmitted to the subscriber line (11).   4 - Subscriber terminal equipment according to any one   of the preceding claims, characterized by the fact that the second   signal (SYN) indicating the synchronization of the terminal equipment (1A) with the associated line circuit (15, 16) in the switching center is produced by a receiving device (197) contained in the unit   central station (237) and processing the signals received from the subscriber line (11).   - Subscriber terminal equipment conforming to any one   of the preceding claims, characterized in that the   switching device (233) is an AND gate.