Background of the Invention

The present invention relates generally to hands-free radio telephone

operation and, more particularly, to an untethered microphone for permitting

hands-free radio telephone communications.

When a handheld radio telephone, such as a cellular telephone, is operated

in a moving vehicle, safety considerations dictate that a hands-free accessory be

used. The hands-free accessory often provides a physical entrapment for the

portable radio telephone, and, among other features, an external microphone

located in a position to pick-up the driver's voice. The physical entrapment for

the portable radio telephone is generally described as a cradle. The external

microphone is typically altached, clipped, or mounted lo the driver's sun-visor or

mounted along the windshield or driver window trim.

Electrical signals from the microphone corresponding to the user's voice

must be coupled to the radio telephone. Currently, this coupling is made via a

cable running between the external microphone and the body of the radio

telephone. When a remote microphone cable is used, the cable must be shielded

in order to prevent the injection of spurious electrical noise into the radio

telephone's audio system. Because of the requirement for shielding, the cable is

relatively thick, and therefore unsightly when strung across the interior of the

vehicle.

In order to hide the cable, it could be built into the vehicle's structure

during manufacture or, as currently done, added by an after-market vendor. Both

of these approaches are inherently unsatisfactory. The first is unsatisfactory

because of the added manufacturing cost, the problem of stressing the cable

whenever the sun-visor is moved, and the problems associated with repairing the

cable once installed. The second approach is unsatisfactory because of the

consumer's well-founded reluctance to allow an after-market technician of

unknown skill to take apart, drill and otherwise modify the vehicle in order to hide

the cable.

Thus, there remains a need for a wireless microphone adapted lo operate in

association with a radio telephone base unit. In order to completely eliminate

associated wiring, there is a need for a remote, wireless microphone having its

own independent power supply. There is also a need for a rechargeable power

supply capable of using solar energy to recharge a battery in the remote

microphone in order to avoid having to periodically replace regular batteries.

Summary of the Invention

The present invention is directed towards an untethered microphone

associated with a radio telephone base and adapted to provide wireless

communication therebetween. The remote microphone may include a

rechargeable battery, a solar power supply, and an associated solar panel

configured to recharge the battery. The remote microphone and base unit are

adapted to each transmit and receive data and control signals therebetween. The

remote microphone is further adapted to transmit voice signals from the

microphone to the base unit during operation. Typically, a first transceiver is

located with the remote unit, and a second transceiver is located with the hands-

free base unit. Working together, the transceivers carry the microphone's signals

to the radio telephone's transmitter. Additionally, the transceivers carry control

information back and forth between the microphone and the hands-free base unit.

The remote unit is typically mounted on the driver's sun-visor, with the

microphone element mounted facing Ihe driver and the solar panel exposed to the

sun through the vehicle's windshield. The solar panel trickle-charges the

rechargeable battery that supplies power for the remote unit.

Since the remote unit has limited electrical power at its disposal, its power

reserves must be conserved. Power preservation is accomplished by configuring

the remote unit to have a low-power or deactivated mode when the remote unit is

not in use. An actuator is mounted on the remote unit for answering incoming

calls and initiating outgoing calls. The actuator is typically used to bring the

remote out of a deactivated state to initiate operation. When a ringer mounted on

the base unit announces an incoming call, the person receiving the call signals

acceptance of the call by switching on the remote microphone unit with the

actuator. The remote unit then sends the microphone's output to the base unit via

the transceivers on the remote unit and base units. In response, the base unit sends

a call-in-progress signal to the remote unit via a return path provided by the

transceivers. The receiver at the remote unit is activated periodically to monitor

the presence of this signal. In one embodiment, the receiver powers down to save

power and periodically awakens lo check for the presence of a call-in-progress

signal while the transmitter of the transceiver stays on in order lo transmit the

microphone signal.

When the call ends, the base unit stops sending the call-in-progress signal.

The receiver senses the absence of the signal after a few failed attempts to receive

it and powers down, having deduced from the signal's absence lhat the call is over.

Alternately, the call acceptance switch or actuator can be made logically bi-stable,

and therefore useful to terminate the call and power down the remote unit. This

same bi-stable switch can be used by the vehicle's operator to power on the remote

unit in preparation for an outgoing call. In such cases, the remote unit will signal

Ihe base unit to prepare for an outgoing call.

The transmission of voice, data and control signals may be carried out by a

wide variety of analog or digital transmission schemes, such as frequency

modulation, amplitude modulation or pulse code modulation. Additionally, a

control signal may be as simple as receiving a certain Irequency. For example, the

call-in-progress signal may be as simple as a single transmitted frequency or as

complex as a digitally encoded data stream on an analog carrier.

These and other aspects of the present invention will become apparent to

those skilled in the art after a reading of the following description of the preferred

embodiments when considered with the drawings.

Brief Description of tlie Drawings

FIGURE 1 is a schematic of a remote microphone unit and an associated

hands-free base unit constructed according to a preferred embodiment of the

present invention;

FIGURE 2 is a more detailed schematic of the remote microphone unit

constructed according lo the embodiment of Figure 1 ;

FIGURE 3 is a perspective view of the remote microphone unit mounted

on a visor of a vehicle; and

FIGURE 4 is a flow chart showing the progress of a call.

Description of the Preferred Embodiments

Referring now to the drawings in general, and Figure 1 in particular, an

untethered, hands-free vehicle communication system, generally designated 10, is

shown constructed according to the present invention. The hands-free

communication system 10 includes two major sub-systems: a remote microphone

unit 12 and a hands-free base unit 14 for providing wireless or untethered

communications with the microphone unit 12.

The hands-free base unit 14 is typically mounted to a vehicle and provided

power by a vehicle power supply 16. The hands-free base unit 14 may be a

cellular telephone base, a cradle configured to receive a radio telephone, or a

separate unit configured to operate between a radio telephone and the remote

microphone unit 12. In any case, the base unit 14 is configured to provide

untethered communications with the remote microphone unit 12. Of course, the

base unit 14 in turn communicates with a cellular telephone system or other radio

telephone system in a conventional fashion.

The remote microphone unit 12 typically includes a power supply 20,

control circuitry 22, a microphone 24, a transmitter 26, a receiver 30 and an

actuator 32. The remote unit control circuitry 22 is operatively associated with the

microphone 24, transmitter 26, receiver 30 and the actuator 32. When a telephone

user invokes hands-free communications, the user will speak into the microphone

24 and typically receive audible communications through a speaker associated

with the base unit 14. The microphone 24 converts the user's voice into electrical

signals for radio frequency transmission by the transmitter 26. The transmitted

microphone signals are designated 42.

The remote unit control circuitry 22 is configured to also provide

information signals for transmission lo the base unit 14. The transmitted

information signals are designated 44. The information signals 44 may include

any suitable variety of status, data, or control information. For example, the

information signal may be a call initiation signal, a call termination, or a call

acceptance signal.

The transmitted microphone signals 42 and the transmitted information

signals 44 are received by a base unit receiver 36. The base unit control circuitry

34 directs the received microphone signals 42 for radio communications to a

cellular base station of a cellular telephone system in a conventional manner. The

base unit control circuitry 34 will also act on the transmitted information signals

44 from the remote unit 12 based upon the content of signals 44. For example, if

the information signal is a call initiation signal, the base unit 14 will respond by

initiating an outgoing call. Similarly, if the information signal is a call termination

signal, the base unit 14 will terminate the call.

The base unit control circuitry 34 and base transmitter 40 are adapted to

provide and transmit base information signals, designated 46, to the remote unit

12. For example, a call-in-progress signal is transmitted from the base unit 14 to

the remote unit 12 to inform the remote microphone unit that a call is in process.

In sum, the receivers and transmitters for the remote unit 12 and the base

unit 14 provide for two-way communication of control information via the

information signals 44, 46 and transmission of the microphone signals 42 from the

remote unit 12 to the base unit 14.

Turning now to Figure 2, there is shown a more detailed schematic of the

remote unit 12. In order to provide a truly untethered remote unit 12, the unit

must contain its own power supply. Preferably, a battery or system of batteries 52

is used to power the remote unit 12. Preferably, the battery 52 is a nicad battery

rechargeable via a trickle charger 50 coupled to a solar panel 48. The solar panel

48 is optimally positioned in order to receive solar energy whenever possible.

When solar energy is provided to the solar panel 48, electric power is provided to

the battery 52 through the charger 50. Given the automotive application, the solar

panel will be a small low-powered panel providing only small amounts of

continuous energy. The charger 50 will typically provide only a trickle charge to

the battery 52 when solar energy is available. The size of the solar panel 48 and

the capacity of the battery 52 are preferably designed so that the battery 52 always

has sufficient charge lo power the unit during normal operation.

In order to conserve power, the remote microphone unit 12 is normally

turned off. The aclualor 32 is used to initially "wake-up" the control circuitry 22

by directly providing momentary power along line 54 to the control circuitry 22

from the battery 52. The control circuitry 22_recognizes the "wake-up" signal and

sends a power control signal 58 to a primary power control 60. The primary

power control 60 directs power from the battery 52 to the various components of

the remote unit 12. The primary control 60 may be a mechanical relay or switch,

or an electronic switch, such as a bipolar or field effect transistor. Furthermore,

there are a variety of integrated circuits which have zero or low power

configurations or states. These integrated circuits may include transmitters,

receivers, control circuitry, or any combination thereof. The power control signal

58 may also be used to power down the remote unit 12.

When the actuator 32 is pressed, the remote unit's control circuitry

transmits a signal to the base unit 14. The actuator 32 may be pressed either to

initiate an outgoing call or to answer an incoming call. In response, the base unit

14 sends a call-in-progress signal to the remote unit 12 through the respective

transceivers. The receiver 30 at the remote unit 12 operates in conjunction with

the control circuitry 22 to monitor for the presence of the call-in-progress signal

sent from the base unit 14. As long as the call-in-progress signal is present, the

remote unit remains powered on. In a preferred embodiment, the remote unit 12

conserves energy further by having the control circuitry 22 periodically power-on

and off the receiver 30 of the remote unit 12. When the receiver 30 is active, the

remote unit 12 monitors for the call-in-progress signal.

When the call ends, the base unit 14 stops sending the call-in-progress

signal. The control circuitry 22 powers down the various components of the

remote unit 12 after sensing the absence of the call-in-progress signal and after a

few failed attempts to receive it through the receiver 30. Alternately, the actuator

32 can be made logically bi-stable, and therefore useful to terminate the call and

power down the remote unit 12. The actuator 32, in a bi-stable state, can be used

by the user to power on the remote unit in preparation for initiating an outgoing

call. Once the call is initiated, the call-in-progress signaling will resume as

discussed above to keep the remote unit 12 powered during the call.

The actuator 32 may be further configured lo provide an actuator control

signal 56 to the control circuitry 22. The control circuitry 22 will recognize the

actuator control signal 56 and react accordingly. The actuator control signal 56

may be used for a variety of signals, such as turning the remote unit on or off,

initiating a call, or terminating a call.

As best seen in Figure 3, the remote unit 12 is preferably mounted on a

visor 66 of vehicle 68 with a remote unit clip or other mounting bracket 64. The

solar panel 48 is positioned to receive sunlight through the windshield 70 while

the microphone 24 is directed towards the passenger seated in seat 69. The base

unit 14 is mounted near or on the console of the vehicle 68. The base unit 14 is

associated with a speaker 72 to enable the user lo hear another party during radio

telephone communication.

The transmitters and receivers of the remote unit 12 and the base unit 14

are preferably integrated transceivers. Working together, the transceivers of the

remote unit 12 and the base unit 14 carry the transmitted microphone signal 42

from the remote unit 12 to the base unit 14 and ultimately to a radio telephone

transmitter (not shown) for radio telephone transmission to a cellular tower,

satellite or other base station.

Referring now to Figure 4, the operation of the remote unit 12 will be

described in greater detail. In use, a ringer typically signals an incoming call. To

accept the incoming call, the user activates the actuator 32 on the remote unit 12

(Block 100). The remote unit 12 powers on (Block 102) and sends a call-

acceptance signal to the base unit 14 (Block 1 4). The remote unit transmits the

audio transmission signal 42 to provide a mic-to-base-unit link to carry the user's

voice to the base unit for further radio telephone communication (Block 106).

Upon receiving the call-acceptance signal (information signals 44), the base unit

14 sends the call-in-progress signal (base information signals 46) to the remote

unit 12. The remote unit 12 monitors the call-in-progress signal from the base unit

14 (Block 108). If the call-in-progress signal is received by the remote unit 12,

the control circuitry 22 and the receiver 30 will go into a low-power state

(Decision 1 10). Preferably, the control circuitry 22 will power down the receiver

30 and then go into a low-power state. The control circuitry 22 may include an

internal clock configured to wake up the receiver 30 periodically (Block 1 12).

Upon wake up, the control circuitry 22 will power on the receiver 30 and listen for

the call-in-progress signal from the remote unit (Blocks 1 14 and 108). The control

circuitry 22 will continue this procedure until the call-in-progress signal is not

received. If the call-in-progress signal is not received, the control circuitry may

fully power down, sleep for another interval and attempt to receive the call-in-

progress signal, or go into a time-out procedure. The control circuitry 22 may

sleep for a select number of intervals before power down due to the absence of the

call-in-progress signal. The control circuitry 22 will eventually completely power

down the remote unit 12 if the call-in-progress signal is not received (Block 1 16).

The remote unit 12 provides various options to terminate a call. The user

may terminate a call from the base unit 14 by simply deactivating the base unit.

The base unit 14 will cease to broadcast the call-in-progress signal, so the remote

unit 12 will power down due to the lack of presence of the call-in-progress signal,

as discussed above. Alternatively, the user may contact the actuator 32 to

terminate the call. The control circuitry 22 will receive the actuator control signal

52, which may be as simple as a switch closure, and transmit a "call over" signal

(information signals 44) to the base unit 14. The base unit 14 will end the call,

and the remote unit 12 will power down.

To initiate an outgoing call, the user will preferably activate the actuator

32. The remote unit 12 will power on as discussed above, and signal the base that

it is preparing for an outgoing call (information signals 44). Although calls may

be initiated from the base unit 14, this would require the receiver 30 of the remote

unit 12 to remain powered, or periodically wake up from a low-power state.

Certain modifications and improvements will occur to those skilled

in the art upon a reading of the foregoing description. It should be understood that

all such modifications and improvements have been deleted herein for the sake of

conciseness and readability but are properly within the scope of the following

claims.