Terminal equipment suitable for use in a plurality of PSTNs

The present invention relates to a terminal equipment for a PSTN, comprising transmitting means for transmitting audio signals to a PSTN.

A telephones and facsimile machines using a public switched telephone network (PSTN) are well-known.

Figure 1 is a block diagram of a facsimile machine.

The facsimile machine in Figure 1 includes a modular jack 10 for connecting it to a telecommunication network, a facsimile unit 20, a telephone circuit unit 30 and a switch 15 for selectively connecting the facsimile unit 20 and the telephone circuit unit 30 to the modular jack 10. The facsimile machine is connected to the PSTN by the modular jack 10.

A diode bridge (BD) 35 supplies a dc voltage to the telephone circuit unit, regardless of the voltage polarity of the signals from PSTN, to power the electronics of the telephone circuit unit 30.

Each of the telephone circuit unit 30 and the facsimile unit 20 further includes a DC feeding circuit (not shown) for supplying a DC voltage. The DC feeding circuit maintains the telephone line connection by continuously supplying a DC voltage to keep the connection between the facsimile machine and PSTN from being disconnected. A ring detector 25 delivers ring signals incoming from the PSTN to a central processing unit (CPU) 24 to notify the CPU 24 of calls from the PSTN. After determining that there is a ring signal, the CPU 24 determines whether the incoming call is a speech call or an incoming facsimile transmission and then selects the telephone circuit unit 30 or the facsimile unit 20.

The telephone circuit 34 processes voice signals incoming from the PSTN and delivers them to a handset 36. The telephone circuit 34 also processes the voice signals, which are input from the handset 36, and delivers them to the PSTN. Also, the telephone circuit 34 controls the magnitudes of the sidetone signals, which are fed back to the handset 36 among the signals input from the handset 36 and transmitted to the PSTN.

A modem 26 decodes the facsimile signals delivered from the PSTN. An impedance matching unit 28 includes a transformer element and a capacitor to match the impedances of the PSTN and the modem 26. Therefore, when the PSTN is connected to the facsimile unit, it enables the facsimile signals and the like to be transmitted and received between the PSTN and the modem 26. The capacitor included in the impedance matching unit 28 prevents the transformer element from being damaged by an excessive DC current and transmits AC signals only.

As integrated circuit techniques develop, the facsimile unit, the telephone circuit unit, and the like, which are mentioned above, can be integrated in a single element. The telephone circuit unit offered in a single element form includes a microphone terminal for receiving voice signals from the handset and a receiving terminal for receiving voice signals from the PSTN. As noted above, a part of the voice signals, which is received from the microphone terminal and transmitted to the PSTN, is fed back to be delivered again to the handset by the receiving terminal.

The physical characteristics of the PSTNs in different countries all differ. Therefore, different country's PSTNs require communication terminal devices that comply with different specifications. The physical characteristics of different PSTNs differ, for example, in the magnitude and frequency characteristics of the voice signals transmitted from handsets to the PSTN, the magnitude and frequency characteristics signals of voice signals and the magnitude of sidetone signals delivered from PSTN to the handset.

Since these specifications differ from country to country, the characteristics of communication terminal devices, such as telephone sets, must be set differently, according to the country in which they are to be used. Although the communication terminal devices have the same functions, different telephone circuit units must be provided for different countries. Consequently, production costs rise. Furthermore, when a malfunction of the communication terminal device occurs in a certain country, a standardized after sales repair service is impossible, since a repair is only possible after understanding each nation's specification for the telephone circuit unit.

Therefore, using the unified telephone circuit unit, a communication terminal device adapted to the physical characteristics of the different telecommunication networks in all nations is required.

A terminal equipment, according to the present invention, is characterised by the transmitting means being configurable to output signals in accordance with the signal requirements of a plurality of PSTNs having different signal requirements.

The terminal equipment may include a microphone with the transmitting means being configured or configurable for transmitting audio signals received from said microphone.

The terminal equipment may include an image scanner for generating facsimile signals with the transmitting means being configured or configurable for transmitting facsimile signals received from said image scanner.

The terminal equipment may include receiving means for receiving audio signals from a PSTN, the receiving means being adaptable for receiving signals from a plurality of PSTNs having different signal requirements. An earphone or speaker may be included with the receiving means being configured or configurable for transmitting received audio signals to said earphone or speaker. A printing means may be included for printing images with the receiving means being configured or configurable for transmitting received facsimile signals to the printing means.

Preferably, the terminal equipment includes memory means storing configuration data for a plurality of PSTNs, user input means and control means, wherein the control means is responsive to operation of the user input means to select configuration data for one PSTN from the memory means and configure the transmitting and/or means in dependence on the selected configuration data.

Additional preferred and optional features are set out in claims 8 to 23 appended hereto.

Embodiments of the present invention will now be described, by way of example, with reference to Figures 2 to 10 of the accompanying drawings, in which: <ul id="ul0001" list-style="none" compact="compact"><li>Figure 1 is a block diagram of a prior art facsimile;</li><li>Figure 2 is a block diagram of a first facsimile machine according to the present invention;</li><li>Figure 3 is a block diagram of a second facsimile machine according to the present invention;</li><li>Figure 4 illustrates a signal packet delivered by an interface unit included in a communication terminal device according to the present invention;</li><li>Figure 5 is a waveform diagram illustrating an exemplary first synchronization pattern for the signal packets shown in Figure 4;</li><li>Figure 6 is a waveform diagram illustrating an exemplary second synchronization pattern of the signal packets shown in Figure 4;</li><li>Figure 7 is a waveform diagram illustrating an exemplary steady-state pattern of the signal packets shown in Figure 4;</li><li>Figure 8 is a waveform diagram illustrating an exemplary idle pattern of the signal packets shown in Figure 4;</li><li>Figure 9 is a waveform diagram illustrating an exemplary third synchronization pattern of the signal packets shown in Figure 4; and</li><li>Figure 10 is a flowchart of a method for adapting the communication terminal device to physical characteristics of telephone networks according to another embodiment of the present invention.</li></ul>

Referring to Figure 2, a communication terminal device 200 comprises a main unit 250, an interface unit 290, and a telephone network adaptor unit 280.

The telephone network adaptor unit 280 manages the physical connection between the communication terminal device 200 and the PSTN. Also, the telephone network adaptor unit 280 detects ring signals from the PSTN and supplies DC current to maintain the connection between the communication terminal device 200 and the PSTN when ring signals are detected. In doing so, the telephone network adaptor unit 280 is in charge of transmitting and receiving analogue communication signals between the communication terminal device 200 and the PSTN. Moreover, the telephone network adaptor unit 280 converts the received analogue communication signals into digital communication signals and transmits the result to the main unit 250 via the interface unit 290. That is, the analogue communication signals received from the PSTN are converted into digital communication signals by the telephone network adaptor unit 280 and delivered to the main unit 250 via the interface unit 290. The configuration and operation of the telephone adaptor unit 280 will now be described in detail.

The interface unit 290 transfers the digital communication signals between the telephone network adaptor unit 280 and the main unit 250. According to international safety regulations, the telephone network adaptor unit 280 and the main unit 250 must be isolated by the interface unit 290. Using elements such as a transformer or a high voltage capacitor, the interface unit 290 delivers digital communication signals between the telephone network adaptor unit 280 and the main unit 250 that are isolated. The digital communication signals can include various control signals as well as digitized analogue communication signals. The digital communication signals will now be described in detail.

The main unit 250 comprises a memory 210, a facsimile unit 220, a central controller 230, a telephone circuit unit 240 and a handset 225. The central controller 230 controls the overall operation of the communication terminal device. When it is determined that an analogue communication signal, received from the PSTN, is a facsimile signal, the facsimile unit 220 processes the received facsimile signal. On the other hand, when it is determined that an analogue communication signal, received from the PSTN, is a telephone signal, the received analogue signals are processed by the telephone circuit unit and delivered to the handset 225. In order to determine whether an analogue signal received from the PSTN is a facsimile signal or a telephone signal, it must be detected whether the handset 225 is off-hook.

The configuration and operation of the telephone circuit unit 240 will now be described in more detail.

The communication terminal device 200 in Figure 2 is connected to the PSTN through the telephone network adaptor unit 280. Also, the telephone network adaptor unit 280 converts the physical characteristics of the analogue communication signals, received from the PSTN, and adapts the communication terminal device to the physical characteristics of the PSTN. For example, the amplitude of the analogue communication signals under the control of the central processor 230 can be altered by changing the gain of an amplifier (not shown) embedded in the telephone network adaptor unit 280. Furthermore, the frequency characteristics of the analogue communication signals can be altered by changing the transfer function, e.g. the pass band, of a digital filter (not shown). Therefore, by only changing the telephone network adaptor unit 280, communication terminal devices having identical telephone circuit units 240 can be adapted to various PSTNs. Moreover, the memory unit 210 can store information regarding the PSTN specifications for all or some nations. In this case, the information on the physical characteristics of the PSTN to which the communication terminal device 200 is connected can be read and the physical characteristics of the analogue communication signals can be changed according to the read information. It is preferable that the information on the physical characteristics of the PSTN is provided as firmware. Then, a user can change the physical characteristics of the analogue communication signals based on the information offered in the firmware, for example by only choosing the name of the nation, without requiring knowledge of the physical characteristics of the PSTN to which his communication terminal device 200 is connected.

Referring to Figure 3, a second communication terminal device 300 comprises a main unit 350, an interface unit 390 and a telephone network adaptor unit 380.

The main unit 350 comprises a memory unit 310, a facsimile unit 320, a central controller 330, a telephone circuit unit 340 and a handset 325. The telephone circuit unit 340 comprises a voice signal processor 342 and a signal converter 344. The telephone network adaptor unit 380 comprises a signal converter 381, a signal characteristic adjustor 383, a ring detector 385, a DC current adjustor 387 and an AC signal processor 389.

The DC current adjustor 387, included in the telephone network adaptor unit 380, controls the amount of DC current incoming from the PSTN to the telephone network adaptor unit. The signal converter 381 converts the analogue communication signals, such as voice or facsimile signals, received from the PSTN by the telephone network adaptor unit, into digital communication signals and converts the digital communication signals received from the interface unit 390 by the telephone network adaptor unit 380 into analogue communication signals and transmits the converted analogue signals to the PSTN. As noted above, the components included in the telephone network adaptor unit 380 are controlled by the central controller 330. The control signals generated by the central controller 330 are transmitted and received between the telephone circuit unit 340 and the telephone network adaptor unit 380 via the interface unit 390. The control signals are digital signals delivered in packets and will be described below in detail.

When there is an incoming call from the PSTN to the communication terminal device 300. That is, when a ring signal from the exchange is received by the communication terminal device 300, the ring detector 385 detects the received ring signal. The ring detector 385 notifies the central controller 330, via interface unit 390, that the ring signal is detected. Then, the central controller 330 generates the control signals, operates the DC current adjuster 387 in the telephone network adaptor unit 380, and connects the communication terminal device 300 to the PSTN. While communication between the PSTN and the communication terminal device 300 is in progress, the analogue communication signals from the calling party, incoming from the PSTN, are received by the AC signal processor 389 in the telephone network adaptor unit 380. The physical characteristics of the analogue communication signals, received by the AC signal processor 389, are changed by the signal characteristic adjustor 383. The signal converter 381 converts the analogue communication signals into digital communication signals and the converted digital communication signals are transmitted to the main unit 350 via the interface unit 390.

The main unit 350 discriminates only voice signals from the received digital communication signals of predetermined form, and restores the analog communication signals using the signal converter 344. The voice signal processor 342 alters the physical characteristics of the voice signals in accordance with the characteristics of the PSTN and transmits them to the handset 325.

The transmission of the voice signals from the handset 325 to the PSTN will now be described in more detail. Voice signals, received by the handset 325, are processed by the voice signal processor 342. The voice signal processor alters the physical characteristics of the received voice signals. The processed voice signals are converted into digital communication signals by the signal converter 344. Then, the converted digital communication signals are transmitted to the telephone network adaptor unit 380 via the interface unit 390. The digital communication signals, transmitted to the telephone network adaptor unit 380, are converted into analogue signals by the signal converter 381. The digital communication signals, whose physical characteristics have been altered by the signal characteristic adjustor 383, are transmitted to the PSTN by the AC signal processor 389.

The physical characteristics of the analogue communication signals transmitted and received between the PSTN and the telephone network adaptor unit 380 are adjusted by the signal characteristic adjustor 383. As noted above, the amplitude and frequency characteristics of the analogue communication signals can be included in the physical characteristics of the analogue communication signals. Each of the amplitude and frequency characteristics are easily altered by changing the gain of an amplifier (not shown) and the frequency pass band of a digital filter embedded in the signal characteristic adjustor 383.

The physical characteristics of the analogue communication signals transmitted and received between the telephone circuit unit 340 and the handset 325 can preferably be changed by the voice signal processor 342 in the telephone circuit unit 340.

In the communication terminal device 300 in Figure 3, the determination on the target unit out of the telephone circuit unit 340 and the facsimile unit 320, to which the digital communication signals received from the telephone network adaptor unit 380 are to be transmitted is as follows. That is, the central controller 330 can determine whether the handset 325 is off-hooked, and then determine whether the digital communication signals are either voice signals or facsimile signals.

When the handset 325 is determined to be off-hook, it can be expected that the user is going to make a voice call, so the digital communication signals are delivered to the telephone circuit unit 340. On the other hand, if the handset 325 is determined to be on-hook, it can be expected that a telephone line has been established between the telephone network and the communication terminal device 300 possibly by a device with an automatic facsimile mode function. In which case, the digital communication signals are delivered to the facsimile unit 320.

The memory unit 310 stores the information regarding the physical characteristics demanded in the PSTN by nations for meeting the requirements of the different telephone characteristics of the specific nations. This information can be offered in firmware or software. Then, without necessarily knowing the physical characteristics of the PSTN, a user can adapt the communication terminal device 300 to the specific PSTN.

Referring to Figure 4, a signal packet delivered by an interface unit, as described above, comprises first through third synchronization patterns SYNC1, SYNC2, SYNC3, first and second data patterns DATA1, DATA2, first and second control patterns CTRL1, CTRL2, first and second duplicate data patterns DATA1bis, DATA2bis, a steady state pattern (SS) and an idle pattern (Idle). The middle row in Figure 4 represents the number of symbols constituting each pattern and the bottom row represents the number of data bits constituting each pattern.

The number of data bits constituting each pattern correspond to two times the number of symbols. The reason is that 2-bit binary data is encoded to represent one symbol for facilitating the prevention of data noise and the maintenance of synchronization. That is, one of the digital communication signal packets transmitted and received by the interface unit 390 in Figure 3 is constituted with 126 symbols in total, and since one symbol is represented by two data bits, the total number of bits in one packet is 252.

Data bits for representing logic '0', logic '1', logic 'A' and logic 'B' are as shown in the table 1. <tables id="tabl0001" num="0001"><table frame="all"><title>Table 1 -</title><tgroup cols="3" colsep="1" rowsep="0"><colspec colnum="1" colname="col1" colwidth="52.50mm" /><colspec colnum="2" colname="col2" colwidth="52.50mm" /><colspec colnum="3" colname="col3" colwidth="52.50mm" /><thead valign="top"><row rowsep="1"><entry namest="col1" nameend="col3" align="center">Data bit representation</entry></row><row rowsep="1"><entry namest="col1" nameend="col1" align="left">Symbol</entry><entry namest="col2" nameend="col2" align="left">Data Bit</entry><entry namest="col3" nameend="col3" align="left">Description</entry></row></thead><tbody valign="top"><row><entry namest="col1" nameend="col1" align="left">0</entry><entry namest="col2" nameend="col2" align="left">01</entry><entry namest="col3" nameend="col3" align="left">logic '0'</entry></row><row><entry namest="col1" nameend="col1" align="left">1</entry><entry namest="col2" nameend="col2" align="left">10</entry><entry namest="col3" nameend="col3" align="left">logic '1'</entry></row><row><entry namest="col1" nameend="col1" align="left">A</entry><entry namest="col2" nameend="col2" align="left">11</entry><entry namest="col3" nameend="col3" align="left">used only for sync.</entry></row><row rowsep="1"><entry namest="col1" nameend="col1" align="left">B</entry><entry namest="col2" nameend="col2" align="left">00</entry><entry namest="col3" nameend="col3" align="left">used only for sync.</entry></row></tbody></tgroup></table></tables>

The patterns constituting signal packets shown in Figure 4 are described below. Figure 5 is a waveform diagram illustrating an exemplary first synchronization pattern of the signal packets shown in Figure 4.

The first synchronization pattern SYNC1 notifies a start point of the digital communication signals. In the waveform diagram in Figure 5, the first synchronization pattern SYNC1 preferably consists of symbol "AABB". Referring to Table 1 above, the symbol "AABB" corresponds to data bits "11110000". As shown in Figure 5, when the logic value of the first synchronization pattern SYNC1 is detected at rising edges of successive clock pulses, the bit values "1111000" are obtained. Since the bit values "11110000" corresponds to the symbol "AABB", the first synchronization pattern SYNC1 is identified, and the start of the digital communication is recognized. The reason for representing the first synchronization SYNC1 by using the symbol "AABB" is that logic 0 and logic 1 cannot occur in series during data or control patterns. If logic 1 or logic 0 occurred in series during the data or control patterns, it would be determined that an error had occurred.

When the first synchronization pattern is identified, the first data pattern DATA1, the first control pattern CTRL1 and the first duplicate data pattern are transmitted sequentially; total of 18 symbols.

The first data pattern DATA1, which is transmitted from a main unit to a telephone network adaptor unit 380 comprises eighteen symbols. The data transmitted to the PSTN via the telephone network adaptor unit 380 from the main unit 350 is transmitted in the form of digital communication signals. The transmitted digital communication signals are restored to analogue communication signals by the signal converter in the telephone network adaptor unit 380 and transmitted to the PSTN. The first data pattern DATA1 includes net data comprising sixteen symbols and an error correction code comprising two symbols.

The first control pattern CTRL1 is transmitted from the main unit 350 to the telephone network adaptor unit 380 and includes eighteen symbols in total. In the telephone network adaptor unit 380, 8-bit registers for a total of 38 can be included. The address of the register whose values are read or changed can be allocated by using the first control pattern CTRL1. For example, the first control pattern CTRL1 can include one symbol of a read/write flag, seven symbols of an address pattern, eight symbols of a data pattern and two symbols of an error correction code. The seven symbols of the address pattern allocate an 8-bit register address, and eight symbols of data pattern represent the values of respective registers.

The first duplicate data pattern DATA1bis has the value identical to that of the first data pattern DATA1. The reason for further including the first duplicate data pattern DATA1bis besides the first date pattern DATA1 is to enhance the error detection efficiency. Therefore, for simplicity of configuration, the first duplicate data pattern DATA1bis can be omitted. When the first duplicate data pattern DATA1bis and the first data pattern DATA1 are not in accord with each other by comparison, it is determined that an error has occurred during transmission. If the main unit 350 does not transmit the first duplicate data pattern DATA1 bis, the telephone network adaptor unit 380 will not transmit the second duplicate data pattern DATA2bis correspondingly.

Figure 6 is a waveform diagram illustrating a second exemplary synchronization pattern among the signal packets shown in Figure 4. The second synchronization pattern SYNC2 is "BBAA". Therefore, referring to the waveform diagram in Figure 6, the second synchronization pattern SYNC2 is identified since the logic values of the second synchronization pattern SYNC2 detected at rising edges of clocks correspond to "00001111". The second synchronization pattern SYNC2 is located at the tail of the data packet transmitted from the main unit 350 to the telephone network adaptor unit 380. When the second synchronization pattern SYNC2 is detected, the telephone network adaptor unit 380 alters the channel from the reception mode to the transmission mode.

Figure 7 is a waveform diagram illustrating a steady-state pattern of the signal packets shown in Figure 4. The steady-state packet represents the time interval from the instance when the second synchronization pattern SYNC2 is identified until the instance when the direction of data transmission is changed. During this period, a driver channel between the main unit 350 and the telephone network adaptor unit 380 is altered. That is, during the steady-state period after the second synchronization pattern SYNC2 is transmitted, the channel of the main unit 350 is altered to reception mode, and in the meantime, the channel of the telephone network adaptor unit 380 is altered from reception mode to transmission mode. Two symbol periods (I, II, III, IV) elapse during one steady state pattern.

After the steady-state packet is transmitted, the second data pattern DATA2 is transmitted from the telephone adaptor unit 380 to the main unit 350. Just as in the first data pattern DATA1, the second data pattern DATA2 comprises eighteen symbols in total. But, according to the setting of a loop monitoring register included in the telephone network adaptor unit, the data can be changed. The data is transmitted from the telephone network adaptor unit 380 to the main unit 350. If loop monitoring register is set to 0, the analogue communication signals (such as modem data, caller indicating information, etc.) received from the PSTN are transmitted to main unit 350 since it is determined that the telephone network adaptor unit 380 is forming an actual loop. If loop monitoring register is set to 1, input ring signals are delivered to the main unit 350, since it is determined that the telephone network adaptor unit 380 is in idle state. The loop monitoring register can be set by the first control pattern CTRL1 transmitted from the main unit 350.

The second control pattern CTRL2 is data transmitted from the telephone network adaptor unit 380 to the main unit 350, and comprises eighteen symbols just as the first control pattern CTRL1. The second control pattern CTRL2 delivers the value of the register included in the telephone adaptor unit to the main unit. If the first control pattern CTRL1 of the main unit is set to 'read' and sent to the telephone network adaptor unit 380, the telephone network adaptor unit 380 can load the 8-bit data read from the requested register and send the data to the main unit 350. Or, if the first control pattern CTR1 of the main unit 350 is set to 'write' and sent to the telephone network adaptor unit 380, the telephone network adaptor unit 380 can write the data on the requested register and load the written value on the second control patter CTRL2 to send it to the main unit 350.

The second duplicate data pattern DATA2bis has the same value as the second data pattern DATA2. If the main unit 350 does not transmit the first duplicate pattern DATA1bis, the telephone network adaptor unit 380 will recognize so and will not transmit the second duplicate pattern DATA2bis, as noted above.

Figure 8 is a waveform diagram illustrating an exemplary idle pattern of the signal packet shown in Figure 4. The idle pattern (Idle) is a time interval from when data is sent from the telephone network adapter unit 380 to the main unit 350 to complete one frame to when next frame is transmitted. In the drawing shown in Figure 8, the idle pattern Idle preferably comprises "BBBB" which correspond to a bit data "00000000".

Figure 9 is a waveform diagram illustrating an exemplary synchronization pattern of the signal packets shown in Figure 4. In the waveform diagram shown in Figure 9, the third synchronization pattern SYNC3 is marked with two symbols of "0B". When the third synchronization pattern SYNC3 is identified, the data packet is recognized to be completed, and a new data packet is transmitted.

Figure 4 through Figure 9 is to be comprehended only as examples. That is, any communication terminal device which includes a separate telephone network adapter unit for connecting to the PSTN, and uses various signal waveforms allowing the device to transmit and receive digital communication signals between the main unit and the telephone network adapter unit is to be understood to be within the technical scope of the present invention.

Figure 10 is a flowchart of a method for adapting the communication terminal device to physical characteristics of various telephone networks according to the present invention.

First, information on or related to the physical characteristics of one or more telecommunication networks is stored in a memory S100. The reason for storing the physical characteristics of a plurality of telecommunication networks is to adapt the communication terminal device by using a simple name of the nation, even when the user does not know the physical characteristics of telecommunication network to which his communication terminal device is connected.

The communication terminal device reads the physical characteristics of the telephone network supplied in firmware, when it is used in a particular country S102. Therefore, the physical characteristics of the analogue communication signals are changed so as to be adapted to the physical characteristics of the telecommunication network S104. As noted above, the communication terminal device to which the method is applied comprises the telephone network adaptor unit separately from the telephone circuit unit which are in charge of the physical connection to the PSTN, so the physical characteristics of the telephone network adaptor unit are changed corresponding to the physical characteristics of the PSTN to which the communication terminal device is connected.

Then, the analogue communication signals from the PSTN are received by the telephone network adaptor unit, and are converted into digital communication signals S106. The converted digital communication signals are delivered to the main unit of the communication terminal device via the interface unit S108.

Whether the delivered digital communication signals are facsimile signals or telephone signals is decided by whether the handset is off-hook S110. That is, when it is determined the handset is off-hook, it is determined that a user is to use telephone functions of the communication terminal device. Therefore, the digital communication signals are processed as voice signals S112. On the other hand, when the handset is not off-hook, since the digital communication signals processed as facsimile signals S114.

The flowchart shown in Figure 10 only depicts processes of receiving and processing analogue communication signals from the PSTN. However, it is certain that incoming voice signals from the handset can be delivered after adapting the communication terminal device to the physical characteristics of the PSTN.

In embodiments of the present invention, a communication terminal device which satisfies the physical characteristic requirements of different telephone networks using the same telephone circuit unit is provided.

In addition, a method for adapting a communication terminal device to the physical characteristic requirements of different telephone networks using the same telephone circuit unit is provided.