EP0864218A1 - Telecommunication system and method enabling a user to get access to automated call processing from a central station operating on pulse dialling mode - Google Patents

Abstract

The present invention relates to a telecommunication system and method enabling a user to get access to automated call processing systems. The system comprises in combination a telephone line interface means adapted to provide the function of a telephone set, a control means connected to the telephone line interface means, and adapted to constantly monitor the telephone line, to analyze a call progress signal and a ring-back tone signal and to switch automatically without human intervention from a pulse-dialling mode to a DTMF-dialling mode upon detection of a ring-back signal validated by a central office. This system also includes a handset and keypad means connected to the telephone line interface means and the control means. The central office processes calls in a pulse-dialling mode. The system enables the user to get access to automated-call processing systems, the access to which is limited to callers equipped with DTMF telephones and central office base DTMF services. The telephone line interface means is adapted to detect the presence of a ring signal on the telephone line, wherein the ring signal is indicating a receiving-call mode. The control means is adapted to detect the presence of a ring-back signal, wherein the ring-back signal is indicating a placing-call mode.

Description

TELECOMMUNICATION SYSTEM AND METHOD ENABLING A USER

TO GET ACCESS TO AUTOMATED CALL PROCESSING FROM A CENTRAL STATION OPERATING ON PULSE DIALLING MODE

TECHNICAL FIELD

The present invention iε related to a telecommunication system, and more particularly to a system enabling automated call processing systems, such as voice mail, tele-banking, voice response, etc. , to interface with central offices operating on pulse-dialling signals.

BACKGROUND ART

U.S. Patent 4,675,902 relates to a high- performance telephone instrument with a combination pulse and tone-dialling capacity. The circuitry permits the placement of a call through a rotary-dial-only system into a second network that is of a tone-only nature.

There is also known U.S. Patent 5,228,079, which relates to a method and apparatus for pulse/tone detection and selection, comprising pulse and tone generators connected to a telephone network, a selector and a controller in communication with said selector for causing said selector to select one of said generators.

There is further known U.S. Patent 3,959,599, which relates to a call-initiation delay arrangement for a digital data switching system, comprising means responsive to call-initiating signals from each calling line for requesting the services of the common control equipment.

At the present time, the convenience that call processing technology (audiotex programs, voice mail and voice response, etc.) has provided people is indispensable. However those systems can be addressed only with DTMF signalling, creating a barrier for the pulse telephone user to experience the benefits of the technology.

The source of this barrier lies in the central offices (COs) , since some COs can process calls in pulse- dialling mode only. Calls which are placed with DTMF signalling will not go through.

The present invention solves this problem and presents a telephone set equipped with special circuitry capable of switching between pulse and DTMF or tone dialling modes automatically.

SUMMARY OF THE INVENTION

Broadly, the present invention comprises a telecommunication system enabling a user to get access to an automated call processing system, said telecommunication system comprising in combination: a telephone line interface means adapted to provide the function of a telephone set; a control means connected to said telephone line interface means and adapted to constantly monitor the telephone line, to analyze a call progress signal and a ring-back tone signal, and to switch automatically without human intervention from a pulse-dialling mode to a DTMF- dialling mode upon detecting a validated central office ring-back signal; and a handset and keypad means connected to said telephone line interface means and said control means; wherein said central office processes calls in a pulse-dialling mode, and wherein said telecommunication system enables the user to get access to said automated call processing system to which access is normally limited to callers equipped with a DTMF telephone and central office DTMF services.

Said telephone line interface means is adapted to detect the presence of a ring signal on said telephone line, wherein said ring signal is indicating a receiving-call mode, and said control means is adapted to detect the presence of a ring-back signal, wherein said ring-back signal is indicating a placing-call mode. In another embodiment, said control means comprises a microcontroller means and a differential amplifier means. Said telephone line interface means may comprise a microprocessor and a pulse dialling means. In yet another embodiment, said microprocessor means further comprises a DTMF generator means adapted to provide the DTMF-dialling mode, and said differential amplifier means is connected to the telephone line and is adapted to detect the presence of the ring-back signal. Said microcontroller means is adapted to monitor and analyze the presence of the ring signal detected by said telephone line interface means, and said microcontroller means is adapted to monitor and analyze an output of said differential amplifier means. In still another embodiment, said microcontroller means when placing a call in a default mode is adapted to provide the pulse-dialling mode; said microcontroller means is adapted to disable said pulse-dialling means and to enable said DTMF generator means after the ring-back signal is detected by said differential amplifier means and after said ring-back signal is analyzed and confirmed by said microcontroller means. The handset means is connected to said telephone line interface means, and said keypad means is connected to said microcontroller means; in said pulse- dialling mode keypad entries will be transferred into pulse signals, and in said DTMF-dialling mode the keypad entries will be transferred into DTMF signals.

The present invention includes also telecommunication method enabling a user to get access to an automated call processing system, such as voice mail or the like, which access is strictly limited to a DTMF-dialling mode, from a central office restricted to processing calls in a pulse-dialling mode. Said method comprises the following steps: constantly monitoring a telephone line; analyzing a tone progress signal on said telephone line; and switching at an appropriate time between the pulse-dialling mode and the DTMF-dialling mode to facilitate the access to said automated call processing system.

The monitoring of said telephone line is provided for detecting a ring signal indicating a receiving-call mode, and the monitoring of said telephone line is provided for detecting a ring-back signal indicating a placing-call mode. In said receiving-call mode the DTMF-dialling mode is activated to allow further DTMF entries, and in the placing- call mode said pulse-dialling mode is first activated at the time that the user initiates their call via said central office operating on the pulse-dialling mode.

In still another embodiment, in said placing-call mode the DTMF-dialling mode is activated after the detection of the ring-back signal is analyzed and confirmed enabling the user to get access to said automated call processing system, and in the receiving mode the DTMF-dialling mode is activated. In said placing-call mode the DTMF-dialling mode is de-activated until the confirmation of the detection of said ring-back signal, wherein said confirmation is indicating that the call has been processed by the central office, and in receiving-call mode the ring signal is detected by a telephone line interface means.

In yet another embodiment, the monitoring and analyzing of said telephone line is provided by a control means, and the detection of said ring-back signal in said placing-call mode is provided by a differential amplifier means incorporated within said control means. Said control means is providing automatic switching between said pulse- dialling mode and said DTMF-dialling mode in response to analysis of the tone progress signal of said telephone line, wherein said tone progress signal is the ring-back signal processed by said central office.

In another embodiment of the present invention, said DTMF-dialling mode is provided by means of a DTMF generator means incorporated within said telephone line interface means, and said pulse-dialling mode is provided by a pulse-dialling means incorporated within said control means. Said telephone line interface means communicates with said control means by means of a set of predetermined commands providing successful operation of all steps of said method, and dialling entries are provided by a keypad means connected to said control means. In said pulse-dialling mode said entries are transferred into pulse-dialling signals, and in said DTMF-dialling mode said entries are transferred into DTMF-dialling signals.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a graphical diagram showing the sequence of steps in a placing-call mode;

Figure 2 is a general block-diagram of the present invention; Figure 3 shows communication lines between a telephone line interface means and a microcontroller means of the present invention;

Figure 4 shows a pulse-dialling means and a microcontroller means of the present invention; Figure 5 shows a handset and keypad means of the present invention;

Figure 6 is a circuit of the preferred embodiment of the present invention; and,

Figures 7 and 8 are flow-charts of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The main principle of the present system is based on analyzing the tone progress signals of the telephone line, and based on that analysis choosing the appropriate time for switching between pulse-dialling mode and tone- or DTMF-dialling mode. While in a placing-call mode the ring- back signal is analyzed and in receiving-call mode the ringing signal is analyzed. The present invention is equipped with special circuitry that constantly monitors the telephone line. When the telephone receives a call the ring signal is detected by its internal circuitry, and upon an "off hook" condition the dialling mode is set to tone or DTMF. An "off hook" condition indicates the user of the telephone has answered the call.

As is shown in Figure 1, in a placing-call mode there is no ring signal on the telephone line. An "off hook" condition has been detected by the circuitry of the telephone, which is an indication that the user will place a call. In this case the initiating-dialling mode will be the pulse-dialling mode since the CO can process only pulse dialling. Once dialling has been terminated, the telephone starts to monitor the telephone line waiting for the presence of the ring-back signal. Upon detection of the ring-back signal the dialling mode is switched into DTMF which permits the user to get access to the application requiring it. In this case, the presence of the ring-back signal is an indication that the call has been processed by the CO and the telephone is ringing at the called-party side.

Referring now to Figure 2, a block diagram of the present invention is shown. It comprises a telephone line interface means connected to a telephone line having Tip and Ring identifications. The system also includes a control means connected to said telephone line and to said telephone line interface means. A handset and keypad meanε iε connected to said telephone line interface means and to said control means. The telephone line interface means comprises a microprocessor means or an integrated circuit means, and a pulse-dialling means or circuit. Preferably, but not necessarily, said microprocessor means comprises a TEA 7090 single-chip device from SGS-Thomson which integrates on one chip the basic functional elements of a telephone set, such as a speech network, a DTMF or tone generator, a ringer, and a microcontroller interface. The control means includes a microcontroller means. The speech network includes transmitter and receiver channels, to which a handset receiver and a handset microphone can be connected.

The DTMF generator is an "on board" generator. Based on codes received from the microcontroller means the correct DTMF signal will be placed on the telephone line.

In this case the microcontroller means supplies the clock of the DTMF generator.

The ringer can generate up to 8 different tones and the volume of the ringer can be controlled through the microcontroller means.

The microcontroller interface of said microprocessor means includes the following input pins and output pins (see Figure 3) by which it communicates with the microcontroller means:

Power supply (VRMC) - this output comprises the

3.5V regulated voltage supply for the microcontroller means.

Ring Indicator Output (RI) - this signal indicates the presence of a ring signal on the telephone line. The control circuitry or the microcontroller means constantly monitors this output pin of the microprocessor means.

Power On (PON) - as soon as the power supply

(VRMC) output exceeds 3.15V, this pin becomes active and indicates that the line current is present. Combined with the reset signal (RESET) the control circuitry validates the

"off hook" condition.

Reset (RESET) - this output becomes high on the first positive edge of PON (power on) and stays high as long as the power supply (VRMC) is greater than 3.15V. Mask (MSK) - is an input pin which should be low during pulse-dialling mode.

DTMF Clock (CLK) - this is the clock for the DTMF generator which is supplied by the microcontroller means.

Serial Byte Interface (DATA and DCL) - are input pins which carry the necessary codes to control the microprocessor means, those codes being: the DTMF and ring frequency codes; the mode codes (dialling, speech, mute, ring) ; and, the configuration codes (mask/no mask, receive gain, ring levels, reset codes) .

Those codes are provided by the microcontroller means of said control means.

Referring now to Figure 4, a pulse dialling means or circuit is shown. It comprises a two-transistor network, which is used to interrupt the loop current and to perform a pulse-dialling mode. The transistor network is controlled by one of the output pins of the microprocessor means which sends the correct number of the make/break pulses based on the pressed keypad key.

The control means of the present invention performs the following functions: Interfacing with the keypad means, and decoding the pressed keys or entries;

Performing the pulse dialling;

Constantly monitoring the telephone line and the RI, PON and RESET pins of the microprocessor means and switching from pulse dialling when there is a ring-back signal or ring signal on the telephone line;

Interfacing with the microprocessor means, and performing control functions (DATA and DCL) .

The control means or circuitry is comprised of the microcontroller means and a differential amplifier means. As is shown in Figure 6 the inputs of the differential amplifier means are connected to the Tip and Ring of the telephone line, and its output is connected to the A/D (Analog-to-Digital) converter input of the microcontroller means. This output is constantly monitored and analyzed for the ring-back signal, which is a very important feature of the present invention.

Preferably, but not necessarily, the control means or the microcontroller means comprises the ST6294 chip from SGS-Thomson, and most of the above-mentioned operations are performed within the microcontroller means using a predetermined set of commands.

As shown in Figure 5, a handset means is connected to the receiving and transmitting channels of the speech network of the microprocessor means.

A keypad means is connected to I/O (input/output) pins of the microcontroller means. The microcontroller means scans the keypad entries, which the user uses to enter numbers. In pulse-dialling mode keypad entries will be transferred into dial pulse, and in DTMF-dialling mode keypad entries will be transferred into DTMF signals. The keypad means is also used to perform last number redial and memory dialling. The present invention operates in two modes which are discussed below: (i) Receiving-call mode:

The microcontroller means constantly monitors RI, PON and RESET signals of the microprocessor means. When the phone is ringing, the RI signal is active indicating the presence of a ring signal on the telephone line. When the user answers the phone (Offhook condition) , the PON and RESET signals of said microprocessor means become active indicating an "off hook" condition to the microcontroller means. Those active RI signals, followed by active PON and RESET signals, represent a valid condition for changing the dialling mode to DTMF. In this case the pulse-dialling circuit is disabled, and the DTMF generator of said microprocessor means is enabled. All keypad entries scanned by the microcontroller means are decoded and sent to the microprocessor means by means of the DATA and DCL signals, so that the microprocessor means places the corresponding DTMF signals on the telephone line. During DTMF- or tone- dialling mode, keypad entries generate DTMF tones. For example, if the user presses "1", the telephone will place the equivalent DTMF signal, which is the combination of two frequencies 697Hz and 1209Hz, on the telephone line. (ii) Placing-call mode:

When the user lifts the handset of the phone to place a call, the PON and RESET signals of the microprocessor means become active indicating an "off hook" condition. The microcontroller means constantly monitors the RI, PON and the RESET pins of the microprocessor means. Active PON and RESET signals, without the presence of an active RI signal, is an indication that the user is placing a call. In this case the telephone has to be in pulse- dialling mode; therefore the microcontroller means disables the DTMF generator of said microprocessor means and activates the pulse-dialling means or circuit. In the pulse-dialling mode the telephone generates dial pulses for each pressed key button. The pulse dialling is achieved through one of the output pins of the microcontroller means which drives the line-break transistor in the pulse-dialling circuit of Figure 4. The number of pulses depends on the sequence of the depressed keys. When the user has finished dialling the number, the microcontroller means startε monitoring and analyzing the output of the differential amplifier meanε of Figure 6. The output signal of said amplifier meanε is an analog signal, and before performing any analysis, the microcontroller means will first convert this signal into a digital format using an A/D converter incorporated on said microcontroller means. After A/D conversion, filtering and a zero-crossing analysis are performed on said signal and as a result of this analysis the presence of a ring-back signal is finally confirmed. Upon the detection and confirmation of the ring-back signal the microcontroller means stops monitoring the output of the differential amplifier means, disables or switches automatically without human intervention the pulse-dialling circuit, and enables the DTMF generator of said microprocessor means. This operation changes the dialling mode of the telephone from pulse into DTMF. During DTMF or tone dialling, keypad entries generate DTMF tones. For example, if the user presses "1", the telephone will place on the telephone line a DTMF signal equivalent to the combination of two frequencies: 697Hz and 1209Hz. The telephone will stay in tone- or DTMF-dialling mode as long aε the user stays in the "off hook" condition. Once the phone goes "on hook" , the microcontroller means will immediately reset the whole process of detection, and analysis will start from the beginning. Figures 7 and 8 are flow-charts of the operational steps of the method, details of which are explained in the chart FLOW CHART DETAILS on the next page.

Thus the present invention allows the user to get access to any automated call processing system including, but not limited to, automated attendant, voice mail, tele- banking, voice response, digital paging, etc. , access to which are limited to callers equipped with a DTMF telephone and central office serviceε based on DTMF.

The telephone according to the present invention can also be combined with many other features, such as speaker-phone, speed dialling or last number redial, without any interference with the proper functionality of the telephone.

It will be obvious to those εkilled in the art that numerouε modificationε of the present invention may be made without departing from the spirit of the present invention which is limited only by the scope of the claims appended hereto.

FLOW CHART DETAILS

Bloc TELEPHONE SET Power On, the program starts here. Bloc SET TIMER A Counter is initialized. This will determine the keypad scanning interval.

Question RI On? Is the Ring Indicator On? Is the telephone ringing? If yes, it means we are receiving a call.

Question RESET On? Is the Reset Indicator On? Is the telephone handset up? If we were receiving a call, it means the call was answered.

Bloc SWITCH TO DTMF Change the Dialling Mode from Pulse to Tone (Touch Tone) .

Bloc SCAN KEYPAD Scan the keypad to check if any number was presεed.

Question DIGIT? Waε a digit pressed?

Bloc DIAL DIGIT+SET TIMER Dial the digit pressed by user and reinitialise the timer.

Bloc TIMER When we are placing a call, this bloc is started any time we complete one period of timer, whatever is the εtate of the system.

Question TIMER=0? Is the Timer Counter=0? Is the period of time expired?

Bloc ANALYZE LINE SIGNAL Take a sample of the line signal and analyze it.

Question RING BACK On? Is the ring back signal on the line? Bloc RESET TIMER Reinitialise timer counter. Bloc RETURN Since this part of the program

(TIMER) is started at the end of a timer period no matter what is the state of the εyεte , thiε bloc goes back to the point where the εyεtem was at the end of the period.

Claims

CLAIMS :

1. A telecommunication system enabling a user to get access to an automated call processing syεte , compriεing in combination: a telephone line interface means adapted to provide the function of a telephone set; a control means connected to said telephone line interface means and adapted to constantly monitor the telephone line, to analyze a call progress signal and a ring-back tone signal, and to switch automatically without human intervention from a pulse-dialling mode to a DTMF- dialling mode upon detection of a validated central office ring-back signal; and a handset and keypad means connected to said telephone line interface meanε and said control meanε; wherein said central office processes calls in a pulse-dialling mode, and wherein said telecommunication system enables the user to get access to said automated call processing system to which access is normally limited to callers equipped with a DTMF telephone and a central office DTMF service.

2. A telecommunication system according to claim 1, wherein said telephone line interface means is adapted to detect a ring signal on said telephone line, and wherein said ring signal is indicating a receiving-call mode.

3. A telecommunication system according to claim 1, wherein said control means is adapted to detect a ring- back signal, and wherein said ring-back εignal iε indicating a placing-call mode.

4. A telecommunication system according to claim 1, wherein said control means comprises: a microcontroller means; and, a differential amplifier means.

5. A telecommunication system according to claim 1, wherein said telephone line interface means comprises: a microprocesεor meanε; and, a pulse-dialling means.

6. A telecommunication system according to claim 5, wherein said microprocessor means further comprises a DTMF generator means adapted to provide the DTMF-dialling mode.

7. A telecommunication system according to claim 4, wherein said differential amplifier means is connected to the telephone line and is adapted to detect the ring-back signal.

8. A telecommunication system according to claim 4, wherein said microcontroller means is adapted to monitor and analyze the ring signal detected by said telephone line interface means.

9. A telecommunication εyεtem according to claim 7, wherein said microcontroller meanε iε adapted to monitor and analyze an output of said differential amplifier means.

10. A telecommunication system according to claim 7, wherein said microcontroller means is adapted to operate in the pulse-dialling mode aε the default mode upon placing a call.

11. A telecommunication εystem according to claim 7, wherein said microcontroller means is adapted to disable said pulse-dialling meanε and to enable said DTMF generator means after the ring-back signal is detected by said differential amplifier means and after said ring-back εignal is analyzed and confirmed by εaid microcontroller meanε.

12. A telecommunication system according to claim 4, wherein the handset means is connected to said telephone line interface means, and wherein said keypad means is connected to said microcontroller means.

13. A telecommunication system according to claim 12, wherein in said pulse-dialling mode keypad entries are transferred into pulse signals, and wherein in said DTMF- dialling mode the keypad entries are transferred into DTMF signalε.

14. A telecommunication method enabling a user to get access to an automated call processing system, the access to which is limited to a DTMF-dialling mode, from a central office restricted to processing calls in a pulse- dialling mode, said method comprising the following steps: constantly monitoring a telephone line; analyzing a tone progresε signal on said telephone line; and switching at an appropriate time between the pulse-dialling mode and the DTMF-dialling mode to facilitate the access to said automated call processing system.

15. A telecommunication method according to claim 14, wherein the monitoring of said telephone line iε provided to detect a ring εignal indicating a receiving-call mode.

16. A telecommunication method according to claim

14, wherein the monitoring of said telephone line is provided to detect a ring-back signal indicating a placing- call mode.

17. A telecommunication method according to claim

15, wherein in said receiving-call mode the DTMF-dialling mode is activated to allow further DTMF entries.

18. A telecommunication method according to claim 16, wherein in said placing-call mode said pulse-dialling mode is firstly activated at the time the user initiates their call via said central office operating on the pulse- dialling mode.

19. A telecommunication method according to claim 18, wherein in said placing-call mode the DTMF-dialling mode is further activated after the detection of the ring-back signal is analyzed and confirmed to enable the user to get access to said automated call processing.

20. A telecommunication method according to claim 18, wherein in said placing-call mode the DTMF-dialling mode is de-activated until the confirmation of the detection of said ring-back signal, said confirmation indicating that the call has been processed by the central office.

21. A telecommunication method according to claim 15, wherein in said receiving-call mode the ring signal is detected by a telephone line interface means.

22. A telecommunication method according to claim 14, wherein the monitoring and analyzing of said telephone line is provided by a control means.

23. A telecommunication method according to claim

21, wherein the detection of said ring-back εignal in said placing-call mode is provided by a differential amplifier means incorporated within said control means.

24. A telecommunication method according to claim

22, wherein said control means is providing automatic switching between said pulse-dialling mode and said DTMF- dialling mode in response to analysis of the tone progress signal of said telephone line, said tone progresε εignal being the ring-back signal procesεed by said central office.

25. A telecommunication method according to claim

21, wherein said DTMF-dialling mode is provided by means of a DTMF generator meanε incorporated within said telephone line interface means.

26. A telecommunication method according to claim

22, wherein said pulse-dialling mode is provided by a pulse- dialling means incorporated within said control means.

27. A telecommunication method according to claim 24, wherein said telephone line interface means communicates with said control means by means of a set of predetermined commands providing successful operation of all stepε of εaid method.

28. A telecommunication method according to claim 22, wherein dialling entrieε are provided by a keypad meanε connected to εaid control means, and wherein in said pulse- dialling mode said entries are transferred into pulse- dialling signals and in said DTMF-dialling mode said entries are transferred into DTMF-dialling signals.

AMENDED CLAIMS

[received by the International Bureau on 31 October 1996 (31.10.96); original claims 1-28 replaced by amended claims 1-19 (4 pages)]

1. A telecommunication system enabling a user to get access to an automated call processing system, comprising in combination: a telephone line interface means adapted to provide the function of a telephone set; a control means connected to said telephone line interface means for placing a default pulse-dialling mode on the line, the control means being adapted: to constantly monitor the telephone line; to transmit an outgoing call signal in the pulse-dialling mode, to analyze the outgoing call signal and to detect a ring-back tone signal in response to the outgoing call signal, to switch automatically without human intervention from the pulse-dialling mode to a DTMF-dialling mode upon detection of a validated central office ring-back signal, and to reset to the pulse-dialling mode upon termination of the telephone call; to receive an incoming call signal, to switch automatically without human intervention to a mode in which any dialling by the user during the call is transmitted in the DTMF-dialling mode, and to reset to the pulse-dialling mode upon termination of the telephone call; and a handset and keypad means connected to said telephone line interface means and said control means; wherein the telecommunication system is capable of interfacing with central offices that process calls only in a pulse-dialling mode, and wherein the telecommunication system enables the user to get access to the automated call processing system when access is normally limited to callers equipped with a DTMF telephone and a central office DTMF service. 2. A telecommunication system according to claim 1, wherein the control means comprises: a microcontroller means; and, a differential amplifier means.

3. A telecommunication system according to claim

1, wherein the telephone line interface means comprises: a microprocessor means; and, a pulse-dialling means.

4. A telecommunication system according to claim 3, wherein the microprocessor means comprises a DTMF generator means adapted to provide the DTMF-dialling mode.

5. A telecommunication system according to claim

2, wherein the differential amplifier means is connected to the telephone line and is adapted to detect the ring-back signal.

6. A telecommunication system according to claim 2, wherein the microcontroller means is adapted to monitor and analyze a ring signal detected by the telephone line interface means.

7. A telecommunication system according to claim 5, wherein the microcontroller means is adapted to monitor and analyze an output of the differential amplifier means.

8. A telecommunication system according to claim 2, wherein the handset means is connected to the telephone line interface means, and wherein the keypad means is connected to the microcontroller means.

9. A telecommunication method enabling a user to interface with an automated call processing system to which access is limited to a DTMF-dialling mode, when a central office restricted to processing calls in a pulse-dialling mode is between the user and the processing system, said method comprising the following steps: constantly monitoring the telephone line; and, for an outgoing call: transmitting an outgoing call signal in the pulse-dialling mode, analyzing the outgoing call signal and detecting a ring-back tone signal in response to the outgoing call signal, switching automatically without human intervention from the pulse-dialling mode to the DTMF-dialling mode upon detection of a validated central office ring-back signal, and resetting to the pulse-dialling mode upon termination of the telephone call; and, for an incoming call: switching automatically without human intervention to a mode in which any dialling by the user during the call is transmitted in the DTMF-dialling mode, and resetting to the pulse-dialling mode upon termination of the telephone call.

10. A telecommunication method according to claim 9, wherein the monitoring of the telephone line is provided to detect a ring signal indicating a receiving-call mode.

11. A telecommunication method according to claim 9, wherein the monitoring of the telephone line is provided to detect a ring-back signal indicating a placing-call mode.

12. A telecommunication method according to claim 9, wherein for incoming calls a ring signal is detected by a telephone line interface means. 13. A telecommunication method according to claim 9, wherein for outgoing calls the monitoring and analyzing of the outgoing call signal is provided by a control means.

14. A telecommunication method according to claim 9, wherein for incoming calls a ring signal is detected by a telephone line interface means, and wherein for outgoing calls the monitoring and analyzing of the outgoing call signal is provided by a control means.

15. A telecommunication method according to claim 13, wherein for outgoing calls the detection of the ring-back signal is provided by a differential amplifier means included in the control means.

16. A telecommunication method according to claim 9, wherein the DTMF-dialling mode is provided by means of a DTMF generator means included within a telephone line interface means.

17. A telecommunication method according to claim

13, wherein the pulse-dialling mode is provided by a pulse- dialling means included within the control means.

18. A telecommunication method according to claim

14, wherein the telephone line interface means communicates with the control means by using a set of predetermined commands.

19. A telecommunication method according to claim 13, wherein dialling entries are provided by a keypad means connected to the control means.