Radio telephone set used as portable set and vehicle-mounted set

Abstract: A radio telephone set comprises switch circuitry (51), a telephone circuit (71) and a battery (81) for portable operation, which battery may be a built-in battery. When the radio telephone set is not mounted on a vehicle, the switch circuitry is not connected to a battery of the vehicle and feeds power from the built-in battery to the telephone circuit. Thus, the radio telephone set can be used as a portable set. When the radio telephone set is mounted on the vehicle, the switch circuitry is connected to the vehicle battery and this connection causes the automatic switching of the power supply to the telephone circuit from the built-in battery to the vehicle battery. Thus, the radio telephone set can be used as a vehicle-mounted, or onboard, set.

Description: BACKGROUND OF THE INVENTION The present invention relate to a radio telephone set and, more particularly, to a radio telephone set which can be used as a portable set and a vehicle-mounted set. Recently, a single radio telephone set has been used as both a portable set and a vehicle-mounted, or onboard, set. When a radio telephone set is used as a portable set, it is powered by a battery attached thereto. When the radio telephone set is used as an onboard set, it is powered by a vehicle battery. A conventional radio telephone set, which will be described later referring to Fig. 1 of the accompanying drawings, has a power supply (PS) terminal and an ignition (IGN) terminal which are connectable not only with the attached battery but also with the vehicle battery. More specifically, when the radio telephone set is used as a portable set, the PS and IGN terminals are connected to the output terminals of the attached battery. When the telephone set is used as an onboard set, the PS and IGN terminals are connected to the terminals of the vehicle battery. Thus, the user must detach the attached battery when using the telephone set as an onboard set. On the other hand, he/she must re-attach the detached battery to the telephone set when using the telephone set as a portable set. This procedure is cumbersome, especially, to those who frequently change the use mode of radio telephone set. In the specification of European patent application No. 84300739.4, which was published under No. 115966 on August 15 1984, there is described a vehicular radio transceiver which is normally powered via a vehicular ignition switch and a transceiver on-off switch, both being closed. A latch circuit senses the receipt of a communication over the transceiver, and produces a latch signal that powers the transceiver despite the opening of either of the switches. An object of the present invention is to provide a generally improved radio telephone set which can be used as a portable set and an onboard set without giving the above-mentioned disadvantage. Another object of the present invention is to provide a radio telephone set which automatically switches power supply between a built-in battery and a vehicle battery by simply mounting or de-mounting the telephone set on or from the vehicle. Yet another object of the present invention is to provide a radio telephone set to be used as portable and onboard sets and having a circuit preventing a battery built therein from overdischarging. In an arrangement to be described, there is provided a radio telephone set which is to be used as a portable set and a set mounted on a vehicle which has a vehicle battery. The radio telephone set comprises a radio telephone circuit which includes a load and a first power supply (PS) terminal and a first ignition (IGN) terminal. The load is provided with power through the first PS terminal. The telephone set also comprises a battery built therein and second PS and IGN terminals. The second PS and IGN terminals are to be connected to the vehicle battery. A power supply terminal (PST) switch is connected to the first and second PS terminals and to the built-in battery. The PST switch connects the first PS terminal to the built-in battery in response to a first control signal and switches the connection of the first PS terminal from the built-in battery to the second PS terminals in response to a second control signal. In a particular arrangement to be described an AND gate has two inputs connected to the second PS and IGN terminals, respectively. The AND gate provides the first control signal when either one or both of the voltages at its inputs are low, and provides the second control signal when both the voltages at its inputs are high. An ignition terminal (IGNT) switching circuit is connected to the second PS terminal, to the first and second IGN terminals and to the built-in battery. The IGNT switching circuit connects the first IGN terminal to the built-in battery when a voltage at the second PS terminal is low and switches the connection of the first IGN terminal from the built-in battery to the second IGN terminal when the voltage at the second PS terminal is high. The extent of the protection to be conferred hereby is to be determined by the terms of the appended claims, interpreted with the aid of the following description and drawings, which disclose the invention which is characterised in the claims, with reference to previously proposed arrangements and, by way of example, to a particular embodiment of the invention. In the drawings:- Fig. 1 shows a block diagram of a conventional radio telephone set with a detachable battery package; Fig. 2 shows a schematic circuit diagram of a car battery and engine key circuit; and Fig. 3 shows a block diagram of a radio telephone set embodying the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT To better understand the present invention, a conventional radio telephone set will first be described with reference to Figs. 1 and 2. In Fig. 1, a radio telephone circuit 11 comprises a load 17 including a transmitter, a receiver, a handset and so on. the load 17 is applied with power through a power supply (PS) terminal 112 and a power switch 16. The power switch 16 is controlled by the output of an AND gate 15. The AND gate 15 has two outputs. respectively receiving a signal through an ignition (IGN) terminal 113 and a diode 18, and an output of a switch circuit 14. The switch circuit 14 includes a manual switch 141 and an inverter 142. A terminal 114 is a common potential terminal. The PS and IGN terminals 112 and 113 are to be connected, respectively, to either the terminals 192 and 193 of a detachable battery package 19 or the PS and IGN terminals 212 and 213 of a car battery and engine key circuit 20 (Fig. 2). The battery package 19 includes a battery 191 whose position terminal is to be connected to both the terminals 192 and 193. When the telephone set is used as a portable set, the battery package 19 is attached to the telephone circuit 11 to thereby connect the PS and IGN terminals 112 and 113 to the battery terminals 192 and 193, respectively. This provides a high level signal to one input of AND gate 15 through the terminals 193 and 113 and the diode 18. In this condition, if the manual switch 141 is closed, the inverter 142 provides a high level signal to the other input of AND gate 15. As a result, the AND gate 15 produces a high level signal which in turn causes the switch 16 to be closed. Thus, power is applied from the battery 191 to the load 17 through the terminals 192 and 112 and the switch 16. When the telephone set is used as an onboard set, the battery package 19 is detached from the telephone circuit 11 and instead the telephone set is attached to a vehicle to connect the PS and IGN terminals 112 and 113 to the PS and IGN terminals 212 and 213 of car battery and engine key circuit 20, respectively (Fig. 2). The circuit 20 includes a car, or vehicle, battery 21 whose position and negative terminals are coupled through a fuse 23 to the PS terminal 212 and directly to a common potential terminal 214, respectively. The circuit 20 also includes an engine key unit 22 which has ACC (accessary), OFF, ON and START terminals 221-224. The ON and START terminals are connected to the IGN terminal 213. If an engine key is positioned on the ON or START terminal, the positive voltage is applied to the IGN terminal 213, resulting in obtaining the same condition above-mentioned with respect to the battery package 19 when a positive voltage is applied to IGN terminal 113. As mentioned earlier, the battery package 19 must be attached to or detached from the telephone circuit whenever the use mode of telephone set is changed. This makes the use of the telephone set cumbersome. The present invention eliminates this disadvantage. In Fig. 3, a radio telephone set according to the invention comprises a radio telephone circuit 71, switch circuitry 51 and a battery 81 built therein. The radio telephone circuit 71 comprises elements similar to those in the conventional telephone set of Fig. 1. The telephone circuit 71 comprises a load 77 including a transmitter/receiver 771 and a handset 772. The load 77 may include other circuits 773 which require power to operate. Power is applied to the load 77 through a PS terminal 712 and a relay switch 76. The relay switch 76 is comprised of an energizing coil 761 and a contact, or armature, 762 and is controlled by the output of AND gate 75. The AND gate 75 has an output terminal connected to the relay switch 76 through an inverter 80. The AND gate 75 also has two input terminals respectively receiving a signal through an IGN terminal 713 and a diode 78, and an output of a switch circuit 74. The switch circuit 74 includes a manual switch 741 and an inverter 742. A terminal 714 is a common potential terminal. Diodes 78 and 79 are provided to prevent the telephone circuit 71 from being damaged in case voltages of the wrong polarity are applied to the PS and IGN terminals 712 and 713. When positive voltages are applied to the PS and IGN terminals 712 and 713, respectively, and the manual switch 741 is closed, the AND gate 75 provides a high level output to the inverter 80 which in turn provides a low level output to one end of the coil 761 of relay switch 76. Since the positive voltage is applied to the other end of coil 761 through diode 79, current flows through the coil 761, so that the contact 762 is closed. As a result, power is applied to the load 77 through the relay switch 76. If the manual switch 741 is open, no power is applied to the load 77 even if positive voltages are applied to the PS and IGN terminals 712 and 713, respectively. The switch circuitry 51 comprises a power supply terminal (PST) switch 53, an ignition terminal (IGNT) switch circuit 54, and AND gate 55, an overdischarge prevention (ODP) circuit 56, and PS, IGN and common potential terminals 512-514. The PST switch 53 is under control of AND gate 55 and has three terminals 531, 532 and 533 connected with the positive terminal of built-in battery 81, the PS terminal 712 and the PS terminal 512, respectively. The IGNT switch circuit 54 comprises two diodes 541 and 542 whose cathodes are connected to each other and anodes are respectively connected to the ODP circuit 56 and to the IGN terminal 531. The switch circuit 54 also comprises a transistor 543 which has a collector connected to the anode of diode 541, an emitter connected to ground and a base connected to the junction of resistors 544 and 545. The resistors 544 and 545 are connected to the PS terminal 513 and the emitter of transistor 543, respectively. The AND gate 55 has two input terminals respectively connected to the PS and IGN terminals 512 and 513, and provides its output to the PST switch 53. The ODP circuit 56 includes a series connection of a resistor 561 and a Zener diode 562. The resistor 561 is connected between the positive terminal of battery 81 and the cathode of Zener diode 562. The anode of Zener diode 562 is connected to the anode of diode 541. The PS and IGN terminals 512 and 513 are to be connected to the PS and IGN terminals 212 and 213 of car battery and engine key circuit 20 (Fig. 2). In operation, when the voltage of built-in battery 81 is greater than a predetermined voltage V z which is determined by the Zener voltage of Zener diode 562, the power is applied from the battery 81 to the anode of diode 541 through the ODP circuit 56. If the voltage of battery 81 falls below the voltage V z , no power is applied from the battery 81 to the anode of diode 541. Thus, the overdischarge of battery 81 can be prevented by setting the voltage V z to a suitable value. Assume that the voltage of battery 81 is greater then the voltage V z and that nothing is connected to the PS and IGN terminals 512 and 513. Since a voltage at the PS terminal 512 is low, the AND gate 55 provides a low level signal to the PST switch 53 to make the terminal 532 contact the terminal 531. Accordingly, power is applied from the battery 81 to the PS terminal 712 of telephone circuit 71. Furthermore, the transistor 543 turns off, so that the positive voltage of battery 81 is applied to the IGN terminal 713 through the ODP circuit 56 and the diode 541. Thus, the telephone circuit 71 operates with power from the built-in battery 81. The radio telephone set can therefore be used as a portable set. Next, assume that the PS and IGN terminals 512 and 513 of switch circuitry 51 are connected to the PS and IGN terminals 212 and 213 of car battery and engine key circuit 20 (Fig. 2), respectively. In this condition, if the engine key is situated at either the ON or START position, a positive voltage is applied from the car battery 21 to the PS and IGN terminals 512 and 513. Since the AND gate 55 receives high level signals at its input through the PS and IGN terminals 512 and 513, it provides a high level signal to the PST switch 53 to make the terminal 532 contact the terminal 533. Accordingly, power is applied from the car battery 21 to the PS terminal 712 of telephone circuit 71. Since a positive voltage is applied to the base of transistor 543, the transistor 543 turns on, so that the voltage of battery 81 is terminated therethrough. On the contrast, the positive voltage at the IGN terminal 513 is applied to the IGN terminal 713 through the diode 542. Thus, the telephone circuit 71 operates with power from the car battery. The radio telephone set can therefore be used as an onboard set. If the engine key is situated at either the OFF or ACC position, a positive voltage from the car battery 21 is applied only to the PS terminal 512. In this case, the terminal 532 of PST switch 53 is connected to the terminal 531, because the AND gate 55 provides a low level signal to the PST switch 53. As a result, power from the battery 81 is applied to the IGNT switch circuit 54. The power thus applied, however, is not applied to the IGN terminal 713, because the transistor 543 turns on due to the positive voltage at the PS terminal 512. The telephone circuit 71 does not therefore operate even if the manual switch 741 is closed. This prevents the car battery from discharging which otherwise occurs by inadvertently keeping the manual switch 741 closed when the car battery 21 is not being charged. It is to be noted that when the engine key is set to the OFF position, the so-called dark current is not so large because only current from the built-in battery 81 flows through the ODP circuit 56 and the transistor 543. More specifically, if the resistors 561, 544 and 545 have resistances of greater than several tens of kiloohms, the dark current can be reduced to smaller than about 1 miliampere.

Claims: A radio telephone set which is to be used as a portable set and a set mounted on a vehicle with a vehicle battery (21), including radio telephone circuit means (71) including a load (77) and first and second terminals (712, 713), the load being provided with power through the first terminal (712), battery means (81) for powering the radio telephone set when used as a portable set, third and fourth terminals (512, 513) for the vehicle battery, the fourth terminal being connected to the vehicle battery through an engine key circuit of the vehicle, and switch circuitry means (51) for selectively switching the vehicle battery (21) and the battery means (81), characterized in that the switching circuitry means (51) includes first switching means (53) connected to the first (712) and third (512) terminals and to the battery means (81) for connecting the first terminal (712) to the battery means (81) in response to a first control signal and for switching the connection of the first terminal (712) from the battery means (81) to the third terminal (512) in response to a second control signal, first gate means (55) having two inputs connected respectively to the third and fourth terminals (512, 513), for providing the first control signal when either one or both of the voltages at the two inputs is low and for providing the second control signal when both the voltages at the two inputs are high, and second switching means (54) connected to the second to the fourth terminals (713, 512, 513) and to the battery means (81) for connecting the second terminal (713) to the battery means (81) when a voltage at the third terminal (512) is low and for switching the connection of the second terminal (713) from the battery means (81) to the fourth terminal (513) when the voltage at the third terminal (512) is high. A radio telephone set as claimed in claim 1 wherein the switch circuitry means (51) further includes overdischarge preventing means (56) connected between the battery means (81) and the second switching means (54) for preventing current from flowing from the battery means (81) to the second switching means (54) when the voltage of the battery means (81) falls below a predetermined voltage. A radio telephone set as claimed in claim 2, wherein the overdischarge preventing means (56) includes a resistor (561) and a Zener diode (562) which are connected in series between the battery means (81) and the second switching means (54). A radio telephone set as claimed in claim 1, wherein the load (77) includes transmitter means (771), receiver means (771) and handset means (772), and wherein the radio telephone circuit means (71) includes power switch means (76) connected between the load (77) and the first terminal (712) for connecting the first terminal (712) to the load (77) in response to a power control signal, manual switch means (74) for manually producing a manual switch signal, and second gate means (75) for producing the power control signal in response to the manual switch signal and to a high level signal at the second terminal (713). A radio telephone set as claimed in claim 4, wherein the second gate means (75) includes an AND gate (75) having two inputs connected respectively to the second terminal (713) and the manual switch means (74), and an output, an inverter (80) being connected between the output of the AND gate (75) and the power switch means (76). A radio telephone set as claimed in claim 1, wherein the second switching means (54) includes transistor means (543) having a base, an emitter and a collector coupled to the third terminal (512), ground and the battery means (81), respectively, first diode means (541) whose anode is connected to the collector and whose cathode is connected to the second terminal (713), and second diode means (542) whose anode is connected to the fourth terminal (513) and whose cathode is connected to the second terminal (713). A radio telephone set as claimed in claim 1, wherein the first gate means (55) includes an AND gate (55). A radio telephone set as claimed in claim 1, wherein the battery (81) for powering the radio telephone circuit means (71) when used as a portable set is a battery (81) built in the radio telephone set. A radio telephone set including battery means (81) for powering the radio telephone set, first, second, third, and fourth terminals (512, 513, 712, 713), the second terminal (513) being connected to a vehicle battery through a vehicle engine key circuit (20), telephone circuit means (71) connected to the third (712) and fourth (713) terminals, and switch circuitry means (51) for selectively switching the battery means (81) and the vehicle battery, characterized in that the switching circuitry means (51) includes first gate means (55) for providing a first switch signal in response to the application of power to the first (512) and the second (513) terminals, first power switch means (53) for selectively connecting the third terminal (712) to the battery means (81) and for switching the third terminal (712) from the battery means (81) to the first terminal (512) in response to the first switch signal, switching means (54) for selectively connecting the fourth terminal (713) to the battery means (81) and for switching a flow of power to the fourth terminal (713) from the battery means (81) to a flow of power from the second terminal (513) to the fourth terminal (713) in response to the application of power to the first terminal (512). A radio telephone set as claimed in claim 9 wherein the switch circuit means (51) further includes overdischarge prevention means (56) connected between the battery means (81) and the switching means (54) for stopping the provision of power from the battery means (81) to the switching means (54) when the voltage of the battery means (81) falls below a predetermined level. A radio telephone set as claimed in claim 10, wherein the overdischarge prevention means (56) includes a series connection of a resistor (561) and a Zener diode (562). A radio telephone set as claimed in claim 9, wherein the telephone circuit means (71) includes a load (77) having a transmitter (771), a receiver (771) and a handset (772), manual switch means (74) for manually producing a manual switch signal, second gate means (75) for providing a second switch signal in response to the manual switch signal and power application to the fourth terminal, and second power switch means (76) for connecting the third terminal to the load in response to the second switch signal. A radio telephone set as claimed in claim 12, wherein the second gate means (75) includes an AND gate (75) connected to the fourth terminal and to the manual switch means (74) for producing an AND gate output in response to the manual switch signal and the application of power to the fourth terminal, and an inverter (80) for inverting the polarity of the output of the AND gate (75) to produce the second switch signal. A radio telephone set as claimed in claim 9, wherein the first gate means (55) includes an AND gate (55) receiving signals from the first (512) and the second (513) terminals for producing the first switch signal in response to the application of power to the first (512) and second (513) terminals. A radio telephone set as claimed in claim 9, wherein the switching means (54) includes a first resistor (544) having two ends, one end thereof being connected to the first terminal (512), a transistor (543) having a base, an emitter and a collector which are connected respectively to the other end of the first resistor (544), ground and the battery means (81), respectively, a second resistor (545) connected between the base and the emitter of the transistor (543), a first diode (541) whose anode and cathode are connected respectively to the collector and the fourth terminal, and a second diode (542) whose anode and cathode are connected respectively to the second (513) and the fourth (713) terminals. A radio telephone set as claimed in claim 9, wherein the battery means (81) is a battery (81) built in the radio telephone set. A method of supplying a radio telephone set with power from one of a battery (81) for the portable operation of the radio telephone set and a vehicle battery, the radio telephone set including a telephone circuit (71) and first, second, third, and fourth terminals (512, 513, 712, 713), the first terminal (512) being selectively connected to the vehicle battery, the second terminal (513) being selectively connected to the vehicle battery through a vehicle engine key circuit (20), characterised in that the method includes the steps of providing a first switch signal in response to the application of power to the first (512) and second (513) terminals, connecting the third (712) terminal to the battery (81) for portable operation in response to the absence of the application of power to the first (512) and second (513) terminals, switching the connection of the third (712) terminal from the battery (81) for portable operation to the first (512) terminal in response to the first switch signal, providing a second switch signal in response to the application of power to the first terminal, providing power to the fourth (713) terminal from the battery (81) for portable operation in response to the absence of the application of power to the first terminal (512), switching the electrical connection of the fourth (713) terminal from the battery (81) for portable operation to the second terminal (513) in response to the second switch signal, and connecting the telephone circuit (71) to the third (712) and fourth (713) terminals. A method as claimed in claim 17 further including the step of stopping the provision of power from the battery for the portable operation of the telephone set when the voltage of the battery for portable operation falls below a predetermined level. A method of supplying power to a radio telephone set from one of a battery (81) for the portable operation of the radio telephone set and a vehicle battery (21), characterised in that the method includes the steps, in response to the absence of the application of power from the vehicle battery (21) to the radio telephone set, of supplying power from the battery (81) for the portable operation of the radio telephone set, and, in response to the application of power from the vehicle battery to the radio telephone set through a vehicle engine key circuit (51), and automatically switching the power supply to the radio telephone set from the battery (81) for portable operation to the vehicle battery (21).

Inventors: TANAKA MITURU, TANAKA, MITURU
Applicants: NIPPON ELECTRIC CO, NEC CORPORATION
Application year: 1989
Main classification: H04M1
IPC codes: H04B1, H04B7