Method and circuit arrangement for adjusting the volume in a mobile telephone

Abstract: Method and circuit arrangement for adjusting the volume in a mobile telephone. The telephone comprises a transceiver unit and on the other hand a physically separate operating device. A dc voltage level (DC) corresponding to the desired volume is adjusted with a potentiometer (1) in the operating device and the level is converted with an A/D-converter (2) into a. corresponding digital control signal. The control signal is read with a microprocessor (3) in the transceiver unit, which further through the hold circuit (4) controls the gain of the audio amplifier (7). A multiplexer (5) may be provided for controlling and selecting a suitable feedback resistor (6) for the amplifier. The A/D-converter can be located in the operating device or in the transceiver unit. When it is located in the transceiver unit the dc voltage level (DC) is transmitted to the transceiver unit, preferably superimposed on the AC-signal received from the microphone, which then is filtered off before the A/D-converter. The connection between the operating device and the transceiver unit may be realized with a cable or a wireless infrared or radio connection.

Description: The present invention relates to a method for adjusting the volume in a mobile telephone comprising a transceiver unit and a physically separated operating device. The invention also relates to a circuit arrangement realizing the method. In mobile telephones, the speaker amplifier is located in the transceiver unit in order to conserve space and power. It is known to use plus and minus buttons to adjust the volume of the speakers. This kind of solution is described in US-A-4 528 696. In this solution, the plus and minus on/off-type switches of a keyboard are connected to the corresponding digital inputs of a microprocessor. The microprocessor gives the volume control information to a D/A converter, which further gives a volume control signal to the receiver. When one of the buttons is pressed, the microprocessor changes the volume control as long as the button is pressed or the minimum/maximum value is achieved. In this solution, the same keyboard, processor and D/A converter is also used for producing signaling tones for the transmitter. In practice, however, it was found that a user experiences difficulties in using these plus and minus buttons. It is, of course, also possible to place the adjusting means directly in the transceiver unit, for example as a potentiometer, but for the user this again results in cumbersome adjustment. It is possible to reduce the number of conductors between the operating device and the transceiver when the speaker amplifier is placed in the operating device, and at the same time audio signal interferences may be reduced. However, this complicates the use of an external speaker and creates inconvenient currents between the operating device and the transceiver. It is an object of the present invention to obviate the above mentioned problems and to provide a method and circuit arrangement which presents the user with a most convenient volume control. To attain this goal, the invention is characterized in that a dc voltage level corresponding to the desired volume is adjusted with circuit means in the operating device, a control signal corresponding to the dc level is provided to be supplied to a microprocessor, the control signal is read by the microprocessor, and the volume is adjusted by the control signal. Preferably an A/D-converter is used to convert the dc level into a control signal. The converter may be located in the operating device or in the transceiver. In the last-mentioned case the dc level is transmitted preferably on the same wire as the audio signal from the microphone, whereby the audio signal is filtered from the dc signal in the transceiver. The characteristic features of the circuit arrangement according to the invention will be accordingly apparent from the claim 13. Preferably a potentiometer or a rotary switch is used to create the dc level in the operating device. The invention and other features and advantages of the invention are described in more detail in the following with reference to the accompanying drawings wherein Figure 1 shows schematically a block diagram of the circuit arrangement according to the invention, Figure 2 shows in grater detail the circuits in the operating device according to an embodiment of the invention, and Figure 3 shows, partly schematically, the transceiver unit to which the operating device of figure 2 is connected. Referring to figure 1 the dc voltage signal (DC) is adjusted between V₁ and V₂ volts, e.g. between 2 and 5 V. The dc level is converted into a digital control signal with the A/D-converter 2. The A/D-converter may be located in the operating device, whereby the signal to be transmitted is in digital form, or the A/D-converter is located in the transceiver unit, whereby the dc signal is transmitted from the operating device to the transceiver. The digital control signal is read by the microprocessor 3, which controls the multiplexer 5, either directly or via the hold circuit 3. This multiplexer connects a suitable resistance 6 into the feedback circuit of the audio amplifier 7. The resistance 6 of the feedback circuit will in turn determine the gain of the amplifier 7. In figures 2 and 3 there is shown in greater detail a circuit arrangement of a mobile telephone provided with a volume control according to the invention. Figure 2 shows an operating device connected with a multiconductor cable to the transceiver unit according to figure 3. Corresponding to figure 1 the potentiometer of the operating device is shown in figure 2 with the numeral 1, with which the dc voltage signal DC may be adjusted between V₁ and V₂ volts. This dc voltage signal is added to the ac voltage signal AC obtained through the microphone amplifier 12 from the microphone 10. The numeral 8 denotes the speaker, 9 the earphone and 11 the earphone amplifier. The dc voltage level DC which is chosen by the user with the potentiometer 1, and the microphone signal AC superimposed on it, are transmitted on the same cable conductor to the transceiver unit, and more precisely to its microprocessor 3. The AC-signal is filtered off in the filter 17 before the microprocessor 3. In the present embodiment the microprocessor 3 also contains the A/D-converter 2 with which the dc level (DC) is converted to a digital control signal. The control signal is connected through the hold circuit 4 to the multiplexer 5, which in accordance with the control signal selects a feedback resistor for the expander/operational amplifier 13. The audio signal from the operational amplifier 13 is connected through the speaker amplifier 7 either to the speaker in the transmitter amplifier unit or to the speaker 8 in the operating device. The audio signal connected to the earphone 9 is taken directly from the amplifier 13 without a speaker amplifier. The transceiver unit further comprises an address hold circuit 14, a RAM memory 15 and an EPROM memory 16, which contains the program controlling the functions of the telephone and which includes the control of the A/D-converter and converts the control signal from the converter into a control signal for the multiplexer. In place of the described potentiometer 1 a rotary switch could of course be used, for example. The A/D-converter may also be located in the operating device, whereby the control signal is transmitted in digital form to the transceiver unit from the operating device. Especially in such a case, a wireless connection or data bus preferably may be used in place of the connecting cable between the operating device and the transceiver. Such a connection is realized by means known per se operating in the infrared band or alternatively by radio. Thereby a microprocessor is suitably provided also in the operating device in connection with the A/D-converter, the microprocessor transmitting the control data to the data bus between the operating device and the transceiver unit.

Claims: Method for adjusting the volume in a mobile telephone comprising a transceiver unit and a physically separated operating device, characterized in that a dc voltage level (DC) corresponding to the desired volume is adjusted with circuit means (1) in the operating device, a control signal corresponding to the dc level is transmitted from the operating device to the transceiver unit, the control signal is read by a microprocessor (3), and the volume is adjusted in the transceiver unit according to the control signal. A method according to Claim 1, characterized in that the dc voltage level is converted to a control signal in an A/D-converter (2). A method according to Claim 2, characterized in that the conversion to a control signal is provided in the operating device. A method according to Claim 2, characterized in that the conversion to a control signal is provided in the transceiver unit. A method according to Claim 3 or 4, characterized in that the dc voltage level or control signal is transmitted to the transceiver unit through a cable. A method according to Claim 5, characterized in that the dc voltage level (DC) is transmitted on the same conductor together with the audio signal (AC) from the microphone. A method according to Claim 3, characterized in that a second microprocessor is used to provide volume control in accordance with the control signal. A method according to Claim 1 or 7, characterized in that a microprocessor controls the gain of the audio amplifier (13, 7) through a multiplexer (5) connected to the microprocessor. A method according to Claim 8, characterized in that the gain is controlled with the multiplexer (5) by selecting an impedance (6) connected in series with the input of the audio amplifier (13, 7). A method according to Claim 3, characterized in that the control signal is transmitted to the transceiver unit via one or more data lines. A method according to Claim 10, characterized in that the transmission is provided as a wireless infrared connection or as a radio connection. A method according to Claim 1, characterized in that the dc voltage level is selected with a potentiometer (1) or a rotary switch. Circuit arrangement for adjusting the volume in a mobile telephone comprising a transceiver unit and a physically separated operating device, characterized in that the operating device comprises circuit means (1) for creating a dc voltage level (DC) corresponding to the desired volume, that the operating device or the transceiver unit includes an A/D-converter (2) for converting the dc level to a digital control signal, and that the transceiver unit comprises a microprocessor (3) for controlling the gain of the audio amplifier (13, 7) in accordance with the control signal. Circuit arrangement according to Claim 13, characterized in that the circuit means of the circuit arrangement for creating the dc voltage level comprises a potentiometer (1) or a rotary switch.

Inventors: LAJUNEN ARI-PEKKA, MALMI KALEVI, LAJUNEN, ARI-PEKKA, MALMI, KALEVI
Applicants: NOKIA MOBILE PHONES LTD, NOKIA MOBILE PHONES LTD.
Application year: 1990
Main classification: H04M1
IPC codes: H04M1, H03G1, H04M19