IE49774B1 - Digital telephone station - Google Patents

Abstract

1. Circuit arrangement for the connection of additional equipment to a digital telephone station (DT) with units (codecs) for the conversion of the voice information in analog signals and vice versa, which are transmitted full duplex via a two wire remotely fed individual subscriber's line (TAL) and with a first line circuit (L1) as interface to the subscriber's line (TAL), whereby the information arriving at the line circuit is forwarded to an interface for the connection of additional equipment and the information arriving from the additional equipment is forwarded to the subscriber's line, comprising a second interface (L2) having a line circuit for the connection of additional equipment, which is identical with the first line circuit (L1) for the subscriber's line (TAL), whereby the information arriving on the subscriber's line (TAL) and appearing at the terminals (a/b) is forwarded to the terminals (a'/b') of the second line circuit (L2), with these terminals an internal line (JAL) for the connection of additional equipment of the digital telephone station (DT) can be connected, the information transmitted from the additional equipment via the internal line (JAL) appearing at the terminals (a'/b') of the second line circuit (L2) is also retransmitted via a processor (VE) to the terminals (a/b) of the first line circuit, whereby the processor (VE), which is used for receiving, evaluation and generation of the received information and the information to be transmitted (for example speech information, signalling, addressing), prevents the retransmission of information, which is exclusively used on the internal line (JAL).

Description

The present invention relates to a digital telephone station with codecs for the conversion of the incoming digital speech information into analogue values and vice versa for the outgoing direction, whereby the speech information is transmitted via the subscriber line radialtyconnected with the telephone exchange and the two-wire subscriber line is used for remote feeding of the digital telephone station with supply current. In the telephone station a line circuit as interface for the subscriber line is provided.

Digital telephone stations as described above are state of the art.

The circuit diagram and the signalling procedure of a digital telephone station is described in detail in the Proceedings 1978 International Zurich Seminar on Digital Communications in chapter D (Subscriber Terminals).

In general a digital telephone station has a line circuit as inter15 face to the subscriber line for the galvanical separation, for the feeding, for the protection against over-voltages and for the conversion of the transmitted and the received information into a digital form and vice versa. Normally a transmitter and a receiver is connected with the line circuit for the transformation of serially incoming information into a parallel information respectively the parallel information into a serial information for the outgoing direction. The transmitter and the receiver are connected also with the common control or processing unit.

With the conmon control a pulse generator is connected, furthermore the conmon control cooperates with the codecs, which are connected with the 77 4 handset containing microphone and speaker. A similar aggangement is shown in Figure 8 on page D 2.4 of the Proceedings of the Zurich Seminar. The shown circuit diagram gives also information about the connection of additional equipment (external equipment interface), for example data terminals, facsimile equipment, etc. Also Figure 2 on page D 4.5 shows connecting means of data equipment of a digital telephone station. The papers do not give any information about the connection and operation of an additional bell, a second telephone station, an answering unit, etc.

The general object of the invention, therefore, is to provide a digital telephone station which can be connected with additional equipment as named above and which can be operated as main station.

According to the present invention there is provided a circuit arrangement for a digital telephone station with equipment (codecs) for the conversion of transmitted digital speech information into analog values and vice versa, whereby the telephone station is connected radially with a superior exchange via a dual wire fully duplex operated subscriber line with external feeding, with a line circuit as interface for the subscriber line, wherein the information arriving via the subscriber line at the terminals of the line circuit is retransmitted to the terminals of a second line circuit, that an internal line connected with these terminals can be used for the connection of additional equipment associated with the subscriber, the information transmitted on the internal line by the additional equipment arriving at the terminals of the second line circuit is also retransmitted to the terminals of the first line circuit and the 4977 4 line circuits are connected with a processing unit for the registration, evaluation and generation of the received and to be transmitted information (speech information, signalling, etc.).

The incoming information from the subscriber line which appears at the terminals of the line circuit is retransmitted to the terminals of a second line circuit whereby an internal line can be connected with the terminals of the second line circuit for the connection of additional equipment assigned to the digital telephone station.

The information on the internal line generated by the individual units of the additional equipment, which appears at the terminals of the second line circuit, is retransmitted to the terminals of the first line circuit for transmission to the exchange via the subscriber line. Both said line circuits are provided with a common processing unit for the registration, evaluation and generation of the received information respectively to the information to be transmitted. This provides a standard interface for all types of additional equipment which con be connected with the internal line because the information (for example PCM-words) arriving on the subscriber line is retransmitted to the internal line respectively the information arriving on the internal line is retransmitted to the subscriber line. Both functions are performed by the line circuits and the common control of the digital telephone station. This concerns the signalling information only as far as the information arriving on the subscriber line is specified for the additional equipment respectively the information is transmitted from the additional equipment for retransmission on the subscriber line. The entire flow of information arriving on the subscriber line is supervised by the common control of the digital telephone station and is retransmitted to the second line circuit. The same applies to the information arriving on the internal line at the telephone station, which is received by the second line circuit, handed over to the common control or processing unit for supervision and retransmitted to the first line circuit for transmission on the subscriber line.

It is another feature of the invention that the information arriving at the terminals of the second line circuit on the internal line is reflected for the outgoing direction at the same terminals for transmission on the internal line. In case a plurality of units of additional equipment ere connected with the internal line which perform an exchange of information, the exchange of information is not performed directly between the different units but always via the telephone station. The latter performs the supervision of the flow of information which arrives at the second line circuit and is handed over to the processing unit. In this case a retransmission to the subscriber line is prevented.

Another feature of the invention is the connection of a second digital telephone station with the internal line by the connection of the terminals of the second line circuit of said station with the terminals of the second line circuit of the first telephone station being operated as main stetion. The standard interface of the internal line renders possible the connection of a second digital telephone station which can be operated bs additional station or as extension whereby in all cases the same type of telephone station can be used as main or second station because the type of operation is determined by the use of the terminals of the first or second line circuit.

Another feature of the invention is a digital connecting box being connected with the internal line whereby the terminals of the latter are connected with the terminals of the second line circuit of the main station. The digital connecting box can be used for the operation of additional equipment for example an additional bell, an answering unit, etc.

Another feature of the invention is the operation of a data terminal in connection with a modem whereby the latter is connected with the terminals of the second line circuit of the main station.

Another feature of the invention is a standard interface for all units of additional equipment which is equally arranged as the interface of the main station i.e. it has a first and a second line circuit. All units of additional equipment (digital telephone station, digital connecting box, modem, etc.] are arranged and connected serially whereby in all cases the second line circuit ofaunit is connected with the first line circuit of the following unit. Viith the second line circuit of the last unit a return unit is connected for the retransmission of the incoming information. By the use of en identical interface a chain arrangement is possible whereby all units can also be operated individually with the main station.

Brief Description of the Drawings The above and other features of the invention will now be described in detail with reference to the accompanying drawing in which: Fig. 1 is a block diagram showing the main station and the additional equipment connected with the internal line, Fig. 2 is a block diagram of the digital telephone station and Fig. 3 is a block diagram showing the chain connection of the main station and the individual units of the additional equipment.

First of all tbe operation of the digital telephone station which are identical ,/t°r galvanic separation between the telephone station and the subscriber line TAL. ~ T bey contain circuits for protection ageinst overvoltages and for the conversion of the form of transmission of the information used on the subscriber and internal lines into a digital representation and vice versa. Both line circuits are connected with a processing unit VE for the registration, evaluation and generation of the information (PCM-words, signalling, etc.). At the interface of the line circuits LI and L2 the processing unit VE is provided with the necessary transmitters and receivers for tne/t«,ansrormation of the outgoing serially incoming information into a parallel form and of the/.ififormation, Which is offered to the interface in parallel form, into a serial form. The I® information arriving at line circuit LI is handed over to the processing unit followed by the retransmission via line circuit L2.

The same applies tn the information arriving at line circuit LE, which is handed over to the processing unit VE and then retransmitted via line circuit L2. The processing unit is provided wi;;b the usual enalog/digital (A/D) and digital/anelog (D/a) converters which ere connected with handset HS containing the usual audio transducers (microphone and speaker). For tbe input of dial information a key pad '.VT is used which is connected with the processing unit VE. A hook switch HU is used for indicating the operational condition of the telephone station. The key pad V.T and the hook switch HU are suoervised by the processing unit VE whereby the generated information collected by a scanning operation is transmitted by the processing unit VE as signalling information as described above. Also connected with the processing unit VE is en optical indicator or display A2 for the indication of the operational condition, toll charging information, etc. Further details of the digital telephone station are described as far as they concern the invention or for a better understanding of the invention.

A digital telephone station DT operated es main station is connected as with a not shown telephone exchange V by a subscriber line TAL via terminals a/b (see Fig. l). An internal line IAL is connected with with the trrrainrls o'/b' of tho telnphnna station DT onaratnri nr main station H, The interne! line is used For the connection of ndriitinnnl equipment nf the mnin stntinn H, fnr example n ilinitnl connecting box DAD for the operation of an ndditionpl boil ZW or en answering unit AB. Also the connection of a second digital telephone station DT operated as second station Z is possible. Furthermore modems M cen be connected for the operation of data terminals DE (data displays, facsimile units, etc.). While the digital connecting box DAD and the modem M are provided only with one interface a'/b', the digital telephone station DT used as second station Z is of the same type as the digital telephone station u DT operated as main station; i.e. the same type of telephone station can either be operated as main or as second station. The type of application can be programmed either by a manual setting of the telephone station or automatically by the detection of the presence (main station) or absence (second station) of the data flow et the terminals a/b since these terminals are unused at the second station.

The exchange of information between the individual units of the additional equipment is not performed directly but in all cases 2Q via the main station H. This means that the information trans-nitted ' y a unit of the additional equipment arriving at the terminals a'/b* of the main station H is retransmitted to the internal line IAL and the connected units. This is the case for example when several data terminals DE are connected which want to exchange information or when the main station H is called by the second station Z operated as extension or the additional bell is used.

The functions of the individual units are demonstrated by operational examples.

Incoming Call When e signalling word containing a call signal appears on subscriber line TAL it is evaluated by the Drocessing unit VE of the main station Η» It causes an audible signel (bell, sound call, etc.) in the main station. The signalling word is also retransmitted to the internal line IAL. It is received and evaluated by the digital connecting box 48774 DAD in the same way as described above causing the additional bell ZW to generate an audible call signal. When a second station Z is installed the coll sounds there also. IF the handset HS is lifted at the main station H the operation of the hook switch HU is detected by the processing unit VE and a corresponding signalling word is transmitted via the subscriber line TAL to the exchange V causing there a termination of the transmission of the cell signal. The incoming speech signals on the subscriber line TAL are converted in the main station H into audible signals at the handset HS and in the opposite direction the generated audio signals from the handset HS are converted into speech signals and transmitted to the exchange V via subscriber linB TAL. All signals are also transmitted to the internal line IAL. Since they are not addressed by the main station H the received information is not converted at the units of additional equipment.

If the handset HS et the main station H is not lifted during the calling condition and an answering unit AB is connected with the digital connecting box DAD the latter answers the call after a predetermined period of time by generating an off-hook signal which is transmitted from the processing unit of the digital connecting box DAD cs signalling word tD the Internal line IAL. The signalling word arrives et the main station H and is there retransmitted on the subscriber line TAL. Together with the signalling word an address was added by the processing unit of the digital connecting box DAD for the designation of the origin. This address was evaluated by the processing unit VE of the main station and was excluded from the retransmission to the subscriber line TAL. The speech information arriving on the subscriber line TAL is retransmitted to the internal line IAL together with an address for marking the receiving unit, i.e. in this case the digitel connecting box DAD respectively the answering unit A5. The same occurs when the handset HS of the second station Z is lifted. The off-hook condition is indicated optically at the mein station H, 9774 Outooino Call 'hen the handset HS is lifted at the main station H the transmission of the respective signalling word is performed to both the subscriber line TAL end the internal line IAL whereby in the latter case an address is added ceusing an optical indication at the second station Z whereby this station cannot enter the call by lifting the handset. The off-hook signal of the main station H causes the generation of a signalling word (proceed to dial) in the exchange V which is received by the main station H and starts the dial tone in the speaker of the handset HS.

The signalling word is also retransmitted to the internal line IAL but without an eddress. The dial information generated by the operation of the key pad WT at the main station H is transmitted to the exchange V and also to the internal line IAL but without address. The later arriving speech signals are converted in the main station H into audio signals, the same applies vice versa to the audio signals generated by the microphone in the handset HS, which are converted into speech signals and transmitted to the exchange V via subscriber line TAL.

When a second (z) digital telephone station is used as extension a refer back operation from the main station H to the second station Z is possible whereby the speech signals are not transmitted to the subscriber line. The operation is initiated by the depression of a special button at the main station H. Also a call transfer can be performed in both directions, i.e. from the main (H) to the second (z) station and vice versa, becau^the speech information in all cases is transmitted to the internal line IAL.

Internal Call When a second (z) digital telephone station is operated as extension, calls between both telephone station can be performed. The off-hook signal is transmitted likewise in ell cases to the exchange V as signalling word in order to mark the subscriber line TAL busy.

The release of all connections as described above is caused by the on-hook information which is generated by the concerning processing unit VE in form nf o signalling word after the detection nf the change cf the hook sv.'itch condition. The signal is transmitted in all cases also to the exchange V in order to mark the idle condition nf the subscriber line, this applies aloo to internal calls.

Data Transmission The set-up of ε connection for data transmission can either be initiated by the main station H or the concerning data terminal DE. The further operations are performed as described above whereby instead of speech signals data signals are transmitted.

One way to operate the described arrangement is to use a one-channel PCM-line as subscriber line TAL for the transmission of the speech signals in form of PCM-words with a bitrate of So kbit/s whereby the PCM-word may consist of a speech section of B bit and a special section of two bit for the transmission of signalling information and data. Further details of the the signalling are not described since they do not concern the invention.

The transmission of information on the lines TAL and IAL is performed by acknowledgement, i.e. the transmission of an information takes place after the receipt of a previous information, whereby the information may be a signalling ward ar a PCM-word. The individual units (DT, DAO, M) are therefore provided with a digital burst mode transmission circuit.

The feeding of the main station H is performed by the exchange V via subscriber line TAL. Tbe terminals a'/b' of the main station H and the internal line IAL are free of feeding current. The power supply of the units of the additional eouipment is performed from the mains A.C. via vol tare converters. In case of a. power failure the min stetion H remains in operating condition.

A different arronoement is shown in Fio, 3. Here also the dipitol connecting box and the modem M ~re provided with identical interfaces es the dinit.il telephone stetinn DT. The internnnnoctinn is mode in such - way, that each unit of the additional equipment ic connected with its terminals r/b with the terminal r'/b' nf the ->recoedinp unit.

This forms a chain arrangement which is terminated by a return unit R which is cnnnccted with the terminals a'/b' of the lest unit. The rrtum unit R retransmits the incnminn information flow originated by the main station H after passing through all units of the additional equipment on the same way. This arrangement allows the connection of several telephone stations DT with the main station H which even renders possible calls between the individual telephone stations of the additional equipment.

The arrangements according to Figs. 1 and 3 can either be operated with a bitrate on the internal line IAL which is equal to the bitrate used on the subscriber line TAL, whereby the interfaces of both lines are equal or the bitrate of the internal line IAL may be lower than the bitrate of the subscriber line TAL, this may allow a greater length of the internal line IAL.

Claims (7)

1. Circuit arrangement for a digital telephone station with equipment (codecs) for the conversion of transmitted digital speech information into analog value and vice versa, whereby the telephone 5 station is connected radially with a superior exchange via a dual wire full duplex operated subscriber line with external feeding, with a line circuit as interface for the subscriber line, wherein the information arriving via the subscriber line at the terminals of the line circuit is retransmitted to the terminals of a second line circuit, an 10 internal line connected with these terminals can be used for the connection of additional equipment associated with the subscriber, the information transmitted on the internal line by the additional equipment arriving at the terminals of the second line circuit is also retransmitted to the terminals of the first line circuit and the line 15 circuits are connected with a processing unit for the respective registration, evaluation and generation of the received and to be transmitted information (speech information, signalling, etc.).

2. Circuit arrangement according to claim 1, wherein the incoming information arriving at the terminals of the second line circuit is 20 retransmitted to the outgoing direction at the same terminals.

3. Circuit arrangement according to claims 1 and 2, wherein an additional digital telephone station is connected with the internal line by the connection of its terminals of the second line circuit with the terminals of the second line circuit of the digital 25 telephone station being operated as main station.

4. Circuit arrangement according to claims 1 to 3, wherein a digital connecting box is connected with the internal line by the connection of its terminals with the terminals of the second line circuit 4-9774 of the digital telephone station being operated as main station and that additional equipment of the main station can be operated via the digital connecting box.

5. Circuit arrangement according to claims 1 to 4, wherein 5 a modem connected with a data terminal is connected with the internal line by the connection of its terminals with the terminals of the second line circuit of the digital telephone station being operated as main station.

6. Circuit arrangement according to claims 1 to 5, wherein 10 all units of additional equipment have the same type of interface as the digital telephone station being operated as main station, that each unit is connected via the terminals of the first line circuit with the terminals of the second line circuit of the preceding unit and that a unit is connected with the terminals of the second line circuit 15 of the last unit which retransmits the incoming signals in the outgoing direction.

7. Circuit arrangement for a digital telephone station substantially as described herein with reference to the accompanying drawings.