GB2237954A - Cellular telephones - Google Patents

Abstract

Apparatus for use with a telephone installed in a vehicle comprises a keypad 1 mounted on the steering wheel 2 and connected to an electromagnetic signal transmitter 4. A suitable receiver 9 is mounted on a fixed part of the vehicle, spaced from the transmitter. A programmable computer means 13, 14 is operative to process the signal from the receiver for supply to the telephone transceiver 17, whereby the telephone may be operated from the keypad. <IMAGE>

Description

Vehicle Telephone Apparatus The invention relates to apparatus for use with a telephone of the type fitted within a vehicle, commonly known as a cellular telephone. When installed within a vehicle, such telephones' usually comprise a hand set having push buttons which are connected to a transceiver. However, when the associated vehicle is being driven, and the driver wishes to use the handset, e.g.

to take or make a telephone call, he must remove at least one hand from the steering wheel. and possibly two hands if he wishes both to hold the handset and press the buttons. This can be very dangerous.

It is one object of the invention to provide apparatus which minimises these dangers, and which may be used with a wide variety of makes of telephone.

According to a first aspect of the invention there is provided apparatus for use with a telephone installed within a vehicle, and comprising; a keypad having a plurality of push buttons to be located on the steering wheel of the vehicle, an electromagnetic signal transmitter connectable to the keyboard; an electromagnetic signal receiver to be mounted on a fixed part of the vehicle spaced apart from the transmitter; programmable computer means operative to process the signal from the signal receiver into a suitable serial code for supply to the telephone transceiver, whereby the telephone may be operated from the keypad on the steering wheel.

Because the telephone maybe operated from the keypad the driver need not remove his hands from the steering wheel, thereby minimising any dangers.

Different makes of telephone require different digital codes to activate the various functions, for example to send or receive a call, or to input or display the individual numbers. The computer means is operative to convert data indicative of the button that has been pressed into a code that the telephone transceiver can read and which can then activate the required function.

Preferably the computer means comprises a microprocessor having a separate programmable eg EPROM memory. The EPROM memory basically contains the program which is acted upon by the microprocessor. The EPROM memory is preferably arranged so that the program may be easily changed so that the apparatus can be used with a different make of telephone. For example the EPROM memory may be received within a socket for easy removal and replacement.

In a preferred embodiment the electromagnetic transmitter and receiver are of the infra-red type and are arranged to transmit a signal in serial form.

In order that the invention may be better understood it will now be described by way of example with reference to the accompanying diagrammatic drawings, in which; Figure 1 is a schematic block diagram of apparatus according to the invention; and Figure 2 a circuit diagram of one of the components of the apparatus of Figure 1.

As shown in Figure 1 apparatus according to the invention comprises a Keypad 1 having a plurality of push button keys mounted on a steering wheel 2 of a vehicle (not shown). Each key is connected via connections 3 on a PCB(not shown) to an infra red signal transmitter 4. The signal transmitter 4 comprises an array of infrared LEDS 5 connected to an integrated circuit of M709 type manufactured by S.G.S Thompson Ltd and arranged in known manner according to the manufacturers instructions. The signal transmitter 4 is operative to convert the parallel incoming data from each of the respective keys of the keypad into a serial form for transmission by the LEDS 5.

The signal transmitter 4, infra red LEDS 5 and keypad 1 are preferably formed as an integral self contained unit to be mounted in the boss of the steering wheel 2 and powered by a small 9 Volt battery 6, and thereby require no seperate wires which could eg: foul the steering column as the wheel is turned.

The remainder of the apparatus is located remote from the transmitter 4, eg fixed to a static part of the steering column or say, the dashboard. An infra red receiving LED 7 is mounted within line of sight of the transmitter 5 and is connected to a pre-amplifier 8 of TDA 2320 type manufactured by S.G.S Thompson Limited and conected in known manner.

The pre-amplifier 8 is operative to boost the signal for supply to a receiver 9 which converts the serial data into a four bit binary output, one bit on each of the four outputs 10. The receiver 9 comprises an integrated circuit of M104 type, connected in known manner.

The four bit binary outputs 10 from the receiver 9 are connected to an input of a binary to hexadecimal decoder 11 of 4514 BE type which decodes the four bit binary output 10 from the receiver 9 into a sixteen bit hexadecimal output 12, or in other words converts a signal which is any decimal number between 0 and 15 in binary into a signal on any one of the sixteen outputs 12 of the decoder 11.

The sixteen outputs 12 are each respectively connected to an input port of a microprocessor cicuit 13 which is itself connected to an EPROM memory 14. A further input 15 is connected from the receiver 9 as an on/off line to switch the microprocessor on or off as required. The microprocessor 13 is of M56747 type and is operative to process the incoming signal which is indicative of the button pressed and convert this into a code in serial form which the telephone transceiver can recognise. A serial data output 16 is connected to the transceiver or telephone transmitter and receiving apparatus 7, and, as shown, in parallel with a handset 18.

The part of the apparatus not connected to the steering wheel may be powered by the 12 volt vehicle battery 19. A so called "handsfree" facility may also be provided, comprising a separate microphone and speaker 20 connected to the transceiver 17, whereby the user can speak to and hear the other caller without removing his hands from the wheel 2, and without touching the handset 18 at all.

The microprocessor circuit 13 and memory 14 is shown in better detail in figure 2.

The sixteen outputs 12 from the binary to hexadecimal decoder 11 are connected to sixteen input lines IL of the microprocessor which are inturn connected to one of sixteen input ports IP.

Each input line IL is connected via a resistor RI to a + 5V supply rail and is normally held high, a signal appearing on the respective input 12 causing the line IL to go low.

The microprocessor is run at 4MHZ by an oscillator or clock C and the input ports IP are therefore scanned every quarter of a millionth of a second so see if one of the input Ports IP has gone low, indicating that a key on the keypad 1 has been pressed.

The microprocessor M is also connected via a data bus DB to a memory means or EPROM 14 of 27C64 type which is preferably removably received within a socket (not shown). The EPROM 14 contains the program which is acted upon by the microprocessor M.

As mentioned previously, different makes of telephone transceivers and handsets require different codes to activate the various functions for exaple to acknowledge the pressing of one of the keys, to send or receive a call, so that the EPROM 14 contains the program which tells the microprocessor which particular code to output in response to the pressing of a particular key. The microprocessor, in effect continuously scans the input ports IP and upon seeing one of them low asks the EPROM 14 for example "Port 11 is low, what do I do now?" The EPROM 14 writes the required code onto the microprocessor which then passes this code to the transceiver 17.Because the EPROM 14 is a separate unit rather than being integral with the microprocessor M, it may be readily replaced with another EPROM 14 containing a different program suitable for a different make of telephone, or alternatively the same EPROM may be reprogrammed. The required program can be readily established by any conpetent programmer and using known techniques. A decoder integrated circuit D of 74LS139 type is connected between the microprocessor M and the EPROM 14 and is operative to prevent the microprocessor M from writing information onto the EPROM, and thereby corrupting the memory and is arranged to enable the EPROM and tell the EPROM when to write information into the microprocessor M.

The microprocessor M outputs a parallel binary output on output ports OP which are held to ground via resistors RO, and are connected to the inputs of an integrated circuit EO of 74HC8G type which comprises an array of exclusive or gates. Integrated circuit EO is arranged to convert the parallel incoming data from its input lines I into serial data on each of three output lines O. These are connected via resistors REO and transistors T1 to a twenty five way socket 25S (only five pins of which are used).

In use, the transceiver 17, is connected to the microprocessor circuit 13 via the 25 way socket 25S. One of the three output lines 0 from the circuit EO are arranged to convey information between the transceiver and the handset 18 (or keypad 1), another line 0 conveys information between the handset or keypad and the transceiver, and the third line 0 is operative to turn the transceiver on or off in response to pressing of the required key on the keypad 1.

The 5 volt supply for the circuit is derived through a transformer T from the vehicle battery 9.

The invention is not limited to the embodiment show, for example the apparatus may be operative to turn on or control apparatus associated with a telephone, such as a fax machine, answering machine, computer etc, or the stereo system.

Claims (4)

1. Apparatus for use with a telephone installed within a vehicle, and comprising; a keypad having a plurality of push buttons to be located on the steering wheel of the vehicle, an electromagnetic signal transmitter connectable to the keypad; an electromagnetic signal receiver to be mounted on a fixed part of the vehicle spaced apart from the transmitter; and programmable computer means operative to process the signal from the signal receiver into a suitable serial code for supply to the telephone transceiver, whereby the telephone may be operated from the keypad.

2. Apparatus according to Claim 1, characterised in that the computer means comprises a microprocessor having a separate programmable memory such as an eprom.

3. Apparatus according to claim 1 or Claim 2, characterised in that the electromagnetic transmitter and receiver are of the infra-red type.

4. Apparatus for use with a telephone installed within a vehicle substantially as described with reference to any of the accompanying drawings.