MOBILE TELEPHONE SYSTEM

Abstract: An interface apparatus (3, 4) suitable for use with a mobile telephone system which includes a base set (2) and a radio transceiver (1), for converting the telephone system to multimode use. The interface apparatus comprises a control unit (3) for selecting various modes of operation of the system and a main unit (4) associated with the control unit. The main unit includes switching means (9) for receiving input, output and control signals passing between the base set (2) and the transceiver (1) and buffer means (11) associated with the switching means (9) for buffering the signals. The switching means (9) operates under command of the control unit (3) for selecting at least one of the modes of operation.

Description: MOBILE TELEPHONE SYSTEM The present invention relates to improvements in Mobile Telephone Systems. In particular the present invention relates H to an interface apparatus for Mobile Telephone Systems. Existing Mobile Telephone Systems (MTS) have several disadvantages when compared with conventional telephone systems, Without accessing and modifying internal circuits of existing MTS such systems cannot be adapted to multi-mode applications 10 such as hands-free mode or use with conventional telephone accessories such as answering machines, facsimile machines, cordless telephones, or to provide a standard computer access terminal, such as an RS232C socket, etc. It may be appreciated that modification and accessing of telephone equipment is • 15 contrary to Telephone Authority regulations in some countries. An object of the present invention is to provide an interface apparatus for existing mobile telephone systems which alleviates the above-mentioned disadvantages. A ' conventional MTS includes a base set/hand set and a 20 radio transceiver. The base set and transceiver are typically interconnected via a multi-pin plug and socket arrangement. The interface apparatus of the present invention includes a main unit and a control unit. The main unit may be connected between the base set and transceiver of an existing MTS. The 25 main unit preferably is connected between the base set and transceiver section by disconnecting the plug associated with the base set from the socket associated with the transceiver, the main unit may incorporate a plug and socket for receiving the socket and plug of the transceiver and base set respectively. 30 The control unit of the present invention preferably «- includes a separate housing. In one form the housing of the control unit may be locatable between the hand set and base * set of the MTS. At least one part of the housing may be contoured or shaped to fit over the top of the base set. A 35 further part of the housing may be contoured or shaped to receive the hand set thereon. The control unit includes control means. The control 38 means may include mode selecting means and master switch means. In one form the control means may also include a hook switch actuating means. The mode selecting means preferably includes one or more switch devices for selecting various modes of operation of the MTS eg. accessory mode, hands free mode, 5 transfer from hand set to hands free etc. The master switch means may comprise eg. an on/off switch adapted to supply power to the interface apparatus of the present invention. The hook switch actuating means, when provided, preferaolv comprises electromechanical means such as a solenoid activated 10 plunger for engaging the hook switch associated with the base set, thus, taking the telephone off the hook. It will be appreciated that when the control unit is located between th-r hand set and base set of the MTS, the hand set does not engage the hook switch associated with the base set. Therefore even 15 with the interface apparatus switched off or deactivated (ie. normal hand set mode) a hook switch actuating means or equivalent arrangement is required to take the telephone off the hook whenever the hand set is lifted from the control unit. The hands free and other, operating modes of the interface **) apparatus of the present invention, also do not re'quire handl:. g of the hand set. In these modes the hook switch may be remotely released via the hook switch actuating means when it is required to take the MTS off the hook. Alternatively the interface apparatus of the present 5 invention includes an off hook/on hook data generator. The hook data generator may be adapted to generate an Off hook * data signal to the transceiver when the MTS is being used in a mode not requiring handling of the hand set. The hook data generator may be provided in any suitable form. In one form 0 the hook data generator includes a serial to parallel convert=_' such as a circuit type 74165. The main unit of the interface apparatus of the present invention may include a separate housing. The housing of the main unit preferably includes a plug for receiving a socket of 5 the transceiver and a socket for receiving a plug of the base set. -The main unit when deactivated may be adapted to provide a 'straight-wire' connection between the base set and 9 transceiver of the MTS. The main unit when activated may be adapted to isolate eg. via suitable switching means, the base set from the transceiver. The main unit includes buffer means. The buffer <rf means may comprise one or more isolating transformers and/or 5 operational amplifiers. The buffer means may be adapted to convey input, output and control signals between the trans¬ ceiver, base set and main unit and between the main unit and an accessory input socket. Preferably, the buffer means associated with the input and 10 output signals comprises a pair of isolating transformers. The isolating transformers may be adapted to isolate input and output signals passing between the transceiver, main unit and/ or the accessory input socket. The buffer means associated with the control signals may 15 comprise one or more operational amplifiers and/or pulse shapers. The buffer means associated with the control signals may be adapted to amplify and/or reform trigger and other control -signals passing between the base set, transceiver and main unit. Power and other controls (such as the AX wire, 20 clock etc.) for the main unit may be provided via the plug and _ socket associated with the base set and transceiver. The main unit may be switched into various modes of operation via the mode selecting means provided with the control unit. In the hands free mode input and output signals may be 25 relayed via the switching means to a hands free circuit. The hands free circuit may be adapted to perform amplification and noise cancelling functions as required for good quality conversation. The hands free circuit may be provided in any suitable form. In one form the hands free circuit comprises a 30 single chip device such as Motorola MC34018. In the accessory mode the main unit may provide a four wire telephone input. In the latter mode the input and output signals may be relayed via the switching means to the accessory input socket. The accessory input socket may be connected to 35 any telephone accessory device having a four wire output. A hybrid convertor may be adapted to convert the four wire input to a standard two wire telephone input-. In the accessory mode the accessory input socket also may 39 be connected to a suitable modem circuit. The modem circuit may be adapted to convert the input/output signals to a standard computer format eg. suitable for connection to an RS232 socket. According to the present invention. there is provided interface apparatus suitable for use with a mobile telephone system including a' base set and a radio transceiver for converting said system to multi-mode use, said interface apparatus comprising: a control unit for selecting various modes of operation for said system and main unit associated with said control unit; said main unit including switching means for receiving input, output and control signals passing between said base - set and said transceiver, buffer means associated with said switching means for buffering said signals, said switching means operating under command of said control unit for __ selecting at least one of said modes of operation. A preferred embodiment of the_present invention will now be described with reference to the accompanying drawings . wherein: ' _ Fig. 1 shows a block diagram of a mobile telephone syste ~ incorporating an interface apparatus according to the princip.es of the present invention; Fig. 2 shows a schematic diagram of a control unit according to a preferred embodiment of"the present invention- Figs. 3a and 3b show a schematic diagram of the main un - of the interface- apparatus according to a preferred embodimer.-. of the present invention; Fig. 4 shows one form of internal loud .speaker connection suitable for use in hands free mode; and Fig. 5 shows one form of external loud speaker connectio. suitable for use in hands free mode. Fig. 1 shows a radio transceiver 1 and base set 2 associated with a standard mobile telephone system. The interface apparatus of the present invention includes a control unit 3 and a main unit shown generally at 4.... In the standard system plug 5 associated with base set 2 and socket 6 associated with transceiver 1 are connected together. The interface apparatus of the present invention is installed by disconnecting plug 5 from socket 6. Main unit 4 of the present invention includes a corresponding socket 7 for receiving plug 5 of the base set 2 and a plug 8 for receiving socket 6 of the transceiver 1. Control unit 3 may be placec on top of base set 2 or in any other convenient location to complete the installation. Control unit 3 includes a plurality of control switches. The control switches may include a master on/off switch for activating main unit 4 and mode select switches for selecting the operating mode for the MTS eg. hands free mode, accessor mode etc. When main unit 4 is activated at least some of the signal carrying conduits between socket 7 and plug 8 are isolated via switching means 9. Switching means 9 is adapted to switch inter alia input/output signals between hands free circuit 10 and an accessory input depending on the mode of operation selected. Buffer means 11 is included to provide suitable buffering for input/outpu't and control signals passing betweer the MTS and the hands free circuit or accessory input. Mode selection is by means of the control switches provided with control unit 3. The main unit includes a hook data generator 12 for providing hook data to the MTS. Hands free circuit 10 is connected to peripherals such as an internal loud speaker (Fig. 4) and pickup microphone (not shown). The hands free circuit 10 may also be connected to the motor-vehicle's stereo loud speakers (Fig. 5). The accessory input may be connected via a four-to-two wire hybrid converter to a standard two wire telephone socket. The telephone socket may receive standard telephone devices such as answering machines, telefax machines, etc. The accessory input may be connected to a modem circuit such as an FSK device AM 7910, to provide a standard RS 232 computer compatible output. The accessory input may also be connected to any telephone accessory device which has been modified to 4 wire operation, such as a cordless telephone. Modified 4 wire accessory devices generally provide a higher level of performance than their two-wire counterparts. The control unit shown in Fig. 2 includes control switches SI, S2 shown normally open or deactivated. Switch SI when activated (S2 deactivated) is adapted to select hands free mode Operation of SI closes contacts 3, 4 and 5, 6 taking pins 1, 2 of plug A to ground. LED 1 lights indicating hands free node selected. Switch S2 when activated (SI deactivated) is adapted to select accessory mode. Operation of S2 closes contacts 3, 4 and 5, 6 taking pin 1 to ground. LED 2 lights indicating accessory mode selected. When switches SI, S2 are both activated neither pin 1 nor 2 are grounded and the control unit transfers to hand set mode. Both LED's light indicating hand set mode selected. It will be appreciated that when switch SI is activated (hands free mode selected), switch S2 may be used to transfer between hands free mode to hand set mode. The control unit incorporates an electret microphone M for use in hands free mode and a volume control potentiometer VC for adjusting volume of received audio in hands free mode. Plug A of the control unit of Fig * . 2 is plugged into socket A shown in Fig. 3a. Hands free mode is selected by activating switch SI {Fig. 2). Activation of switch S2 operates relays RLY1 and RLY2. Operation of relay RLY1 disconnects input (lines 12, 34) and output (lines 9, 10) signals from the base set and connects these to a respective winding of isolating transformers Tl, Tl respectively. Operation of relay RLY2 connects one terminal of the other winding of each isolating transformer Tl, T2 to common ground. The other terminals (input and output) of the winding are connected to the "receive input" terminals (pins 7, 27) and "output transmit" terminals (pins 4, 5) of voice switched speaker phone (hands free) circuit IC7. IC7 preferably comprises a Motorola type MC 34018. Operation of relay RLY2 results in a logical low at pin 18 of IC7 thereby enabling th- hands free circuit (IC7). Because the base set is 'on hook 1 in the hands free of accessory modes it is necessary during such modes to disconnect thoselines carrying hook ' data signals from the base set to the transceiver. The main unit of the interface apparatus includes a hook data generator for generating on hook/off hook data during the hands free and accessory modes of operation. It will be appreciated that the specifics of hook data generator depends on the type of MTS. The hook data generator described hereinafter and shown in Fig. 3b is suitable for use with the NEC "white phone" MTS, Model No. TR5E120-1B/EZ-440-A, (transceiver/handset). Operation of the hook data generator shown in Fig. 3b is as follows: When switch SI is activated (hands free mode) hook relay RLY3 (Fig. 3a) operates. Hook relay RLY3 also operates in the accessory mode via hook control connection (pin 6) at accessory input socket B. When hook relay RLY3 operates its contacts 1, 2 close supplying power to flip flop 3b (Fig. 3b) and causing its input (pin 13) to go high. Flip flop 3b acts as a debouncer and pulse shaper. When the output of flip flop 3b (pin 9) changes state monostable 4a is triggered. This causes the output of monostable 4a (pin 7) to go low for a period of approximately 7-8 clock cycles of IC1, a parallel to serial converter. It also enables tristate inverting buffers 2a-2f. When the output of flip flop 3b goes low it also triggers change over swithes 5a-5b via control pins 10, 9. This connects pin 15 to pin 1 at switch 5a and pin 4 to pin 3 at switch 5b. In the unswitched state switch 5a connects pin 15 to pin 2 and switch 5b connects pin 14 to pin 5. In the unswitched state therefore switches 5a-5b connect the interrupt and ready lines (7, 8) of the transceiver and hand set units as required for hand set mode operation. When the hand set does its regular update (every 50-60 seconds) the interrupt line (7) goes low at pin 4 of switch 5b causing monostable 4b to trigger and go low for several clock cycles at its output (pin 9). This causes the ready line (8) at the hand set to go low thus fooling the hand set into sending its data along the data line. Since the transceiver never receives the interrupt pulse from the hand set the transceiver's data port is closed and the data is ignored. When buffers 2a-2f are enabled, pin 5 of buffer 2b goes low because the ready line at the transceiver is normally higr.. When the ready line of the transceiver goes low, pin 3 of buffer 2a also goes low. This change of state atpn 3 of buffer 2a causes a short duration low pulse at pin 1 of parallel to serial converter IC1. The latter causes parallel to serial- converter IC1 to load in data from pins 3-6 and 11-14. This data represents an "off hook" or "on hook" signal depending on the state of hook relay RLY3. IC1 is clocked by divide by two divider 3a (a flip flop}. A 1200HZ clock signal received at line 23 of the MTS system is buffered by buffer 2e and divided by divider 3a resulting in _ 600HZ signal at pin 2 of IC1. When IC1 has loaded it data and the ready line (pin 8) of the transceiver goes low, parallel- to serial converter IC1 sends a:seria.l__pαls.e_txain--V-ia pin 9 and inventing buffer 2f o the data line (30) of the MTS system. The transceiver thus is advised that the interface apparatus is "on hook-" or "off hook" and responds appropriately. The transceiver requires an off hook signal to be received at each update to enable a call to proceed. It may be noted that if at any time switch SI is release in hands free mode hook relay RLY3 will change state causing the call to hang up or end immediately. Relay RLY3 will not change state providing that switch SI remains activated (hands free mode). This enables a call to be transferred from hands free mode to hand set mode by activating switch S2. In the circuit shown in Fig. 3b parallel to serial converter IC1 comprises a circuit type 74165. Tristate buffers 2a-2f comprise a circuit type 8096. Flip flops 3a-3b comprise a circuit type 7474. Monostables 4a-4b comprise >a circuit type 5428 and change over switches 5a-5b comprise a circuit type 4053. The circuits shown in Figs. 3a and 3b are interconnected via jumper connectors Jl, J2 as marked. Power to the circuits shown in Fig. 3a-3b is switched via main power relay RLY4 and regulated via regulators REG1, REG2. REG1 comprises a circuit type LM317LZ and REG2 comprises a circuit type 7805. An internal loudspeaker SPK1 (refer Fig. 4) is connected to hands free circuit IC7 via jumper connections J3. An external loudspeaker may be connected to hands free circuit IC7 via socket C which automatically disconnects the internal loudspeaker SPK1. Fig. 5 shows an arrangement for connecting the hands free circuit IC7 to a motor vehicle's own stereo system. The circuit of Fig. 5 is plugged into socket D (Fig. 4). Relay RLY5 operates when relay RLY2 (Fig. 3a) operates. This causes the vehicles stereo loudspeaker to be disconnected from the stereo system and connected in place of internal loudspeaker SPK1. Accessory mode is selected by" activating switch S2 (Fig. 2). Activation of switch S2 causes LED2 to light and.operates only relay RLY1. This connects input and output signals to and from the transceiver unit via isolation transformers Tl. T2 and accessory input socket B to an accessory device. Socket B provides a full 4 wire circuit, (pins 1, 3, 5, 7) a trigger when the MTS rings via the AX wire (pin 2), ground (pin 8) ' , positive 12 volts switched (pin 4) available via relay RLY4 when the MTS is turned on and a hook control to the hook relay RLY3. A four wire to two wire converter can be plugged into input socket B if a standard commercial two wire outlet is required. This may permit telephone accessory devices such as answering machines, cordless telephone (with or without dial out facility), computer modems etc. to be used with the interface apparatus of the present invention. However performance may be obtained by bringing out for wire circuits in such equipment for direct connection to accessory socket B. The interface apparatus of the present " invention may be incorporated with commercial telephone accessory devices in an integrated form. For example the interface apparatus may be integrated with a cordless telephone (with or without dial out facility) and sold- as a package for connection to an existing MTS . It will be appreciated that various alterations, modification and/or additions may be introduced into the constructions and arrangements of parts previously described without departing from the spirit or ambit of the present invention. GP

Claims: THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS: 1. Interface apparatus suitable for use with a mobile telephone system including a base set and a radio transceiver for converting said system to multi-mode use, said interface apparatus comprising: a control unit for selecting various modes of operation for said system and amain unit associated with said control unit:; said main unit including switching means for receiving input, output and control signals passing between said base set and said transceiver and buffer means associated with said switching means for buffering said signals, said switching means operating under command of said control unit for selecting at least one of said modes of operation. 2. Apparatus according to claim 1 wherein said main unit includes a hands free circuit and said control unit is adapted to select a hands free mode. 3. Apparatus according to claim 2 wherein during said hands free mode said control unit causes said switching means to switch said input and output signals to said hands free circuit. 4. » Apparatus according to claim 1, 2 or 3 wherein sai ' main unit includes an accessory input and said control unit is adapted to select an accessory mode. 5. Apparatus according to claim 4 wherein during said accessory mode said control unit causes said switching means :o switch said input and output signals to said accessory input. 6. Apparatus according to any one of the preceding claims wherein said main unit includes a hook data generator and wherein said control unit is adapted to cause said generator to supply hook data to said transceiver during at least some -of said modes of operation. 7. Apparatus according to claim 6 wherein said hook data generator includes a parallel to serial converter. 8. Apparatus according to any one of the preceding claims wherein said buffer means includes isolating transformers for buffering said input and output signals. 9. Apparatus according to any one of the preceding claims wherein said switching means includes a relay for receiving said input and output signals. 10. Apparatus according to claim 9 wherein said switching means includes a change over switch for interrupting said control signals passing between said base set & said transceive . 11. Apparatus according to claim To when appended to claim 6 wherein said hook data generator is adapted to supply hook data to said transceiver when passage of said control signals is interrupted. 12. Apparatus according to claim 1 substantially as herein described with reference to the accompanying drawings. 13. A telephone accessory device incorporating apparatus according to any one of the preceding claims. 14. A cordless telephone incorporating apparatus according __ any one of claims 1-12.

Inventors: FREEMAN ANTHONY, MASSA MASSIMO, FREEMAN, ANTHONY, MASSA, MASSIMO
Applicants: CUSTOM PROD DEV, CUSTOM PRODUCT DEVELOPMENT PTY. LTD.
Application year: 1986
Main classification: H04Q7
IPC codes: H04M1, H04W88