WO1999009665A1

WO1999009665A1 - Handset for half-duplex communications through a cellular terminal

Info

Publication number: WO1999009665A1
Application number: PCT/US1998/016838
Authority: WO
Inventors: Thomas Anthony Przelomiec; Robert J. Blaser; Seyed Tabaian
Original assignee: Ericsson Inc.
Priority date: 1997-08-14
Filing date: 1998-08-12
Publication date: 1999-02-25
Also published as: AU9104598A

Abstract

An accessory apparatus and an associated method are disclosed for providing half-duplex communications through a full-duplex cellular terminal. The cellular terminal outputs a speaker signal and receives a microphone input signal. The accessory apparatus includes a speaker, a microphone, and a switch. The speaker broadcasts the speaker signal from the cellular terminal to a user. The microphone generates the microphone input signal which is provided to the cellular terminal. The switch has a first operation state and a different second operation state. In the first operation state, the switch electrically connects the speaker signal from the cellular terminal to the speaker while substantially electrically isolating the microphone input signal output, which is output by the microphone, from the cellular terminal. In the second operation state, the switch electrically connects the microphone input signal from the microphone to the cellular terminal while substantially electrically isolating the speaker from the speaker signal which is output by the cellular terminal. The switch transitions between the first state and the second state in response to a user's input to provide half-duplex communications through the full-duplex cellular terminal.

Description

HANDSET FOR HALF-DUPLEX COMMUNICATIONS THROUGH A CELLULAR TERMINAL

FIELD OF THE INVENTION

The present invention relates generally to cellular communications systems and, more particularly, to a handset accessory which provides half-duplex communications through a full- duplex cellular terminal.

BACKGROUND OF THE INVENTION In cellular communication systems, a base station communicates across a control channel and voice channels with mobile terminals which are within the cellular area of the base station. During a cellular call, the base station assigns a voice channel to a mobile terminal and maintains full-duplex communications with the mobile terminal across the voice channel. Group cellular calls have been proposed in which several terminals are assigned the same voice channel so that audio signals are broadcast between the grouped terminals. For time-division multiple access (TDMA) systems, terminals within a group are assigned the same time-slot on a shared voice channel. With full-duplex communications between the terminals in the group, background noise and audio signals from any simultaneously speaking users can combine to render communications within the group confusing and unintelligible.

The relatively low sound level from a terminal rapidly drops below the hearing threshold of a user as the terminal is moved away from the user's ear. Consequently, a user can monitor communications within the group call only by holding the terminal adjacent to the user's ear. However, in public safety operations, such as police or fire, it is desirable for a user to passively monitor group communications from a remotely located mobile terminal, such as when the mobile terminal is attached to a waist belt.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide half-duplex communications through a full-duplex cellular phone .

It is a further object of the present invention to enable a user to monitor communications on a remotely located cellular telephone . It is a further object of the present invention to facilitate group calling features on a cellular telephone.

These and other objects are addressed by a push-to-talk (PTT) controller which is connected to a full-duplex mobile cellular terminal. The cellular terminal outputs a speaker signal and receives a microphone input signal. The PTT controller includes a speaker, a microphone, and a switch. The speaker broadcasts the speaker signal from the cellular terminal to a user. The microphone generates the microphone input signal which is provided to the cellular terminal. The switch has a first operation state and a different second operation state. In the first operation state, the switch electrically connects the speaker signal from the cellular terminal to the speaker while substantially electrically isolating the microphone input signal, which is output by the microphone, from the cellular terminal. In the second operation state, the switch electrically connects the microphone input signal from the microphone to the cellular terminal while substantially electrically isolating the speaker from the speaker signal which is output by the cellular terminal. The switch transitions between the first state and the second state in response to a user' s indicated desire to transmit an audio signal through the cellular terminal .

In this manner, the PTT controller provides half-duplex audio communications through the full-duplex cellular terminal. Consequently, users can monitor audio communications by one or more other users within a group call while the microphones, in terminals with which users are not depressing the switches, are muted to minimize noise in the communicated signals. Moreover, the user can monitor broadcasted communications by the speaker while the PTT controller and cellular terminal are remotely located from the user.

BRIEF DESCRIPTION OF THE DRAWINGS For a more complete understanding of the present invention and the further advantages thereof, reference is now made to the following Detailed Description, taken in conjunction with the Drawings, in which:

Fig. 1 is a perspective view of a prior art mobile cellular terminal; Fig. 2 is a front view of the connector which is shown in Fig. 1;

Fig. 3 is a perspective view of a push-to-talk (PTT) handset accessory according to the present invention; and

Fig. 4 is a circuit diagram of the PTT handset which is shown in Fig. 3.

DETAILED DESCRIPTION OF THE INVENTION A prior art mobile cellular terminal 10 is shown in Fig. 1. The terminal 10 includes a housing 12 in which a speaker 14, a microphone 16, and an accessory connector 18 are disposed. A battery 20 is releasably connected to the terminal 10.

With reference to Fig. 2, the conventional connector 18 includes 12 electrical contacts 22. The contacts 22 include a power contact 24, a ground contact 26, a speaker output contact 28, a microphone input contact 30, an audio ground contact 32, a hook contact 34, a data output contact 36, and a data input contact 38. The connector 18 further includes windows 42.

The power contact 24 and the ground contact 26 are electrically connected to the battery 20 (Fig. 1) . The speaker output contact 28 is electrically connected to conventional speaker circuitry within the housing 12 which provides an audio signal to the speaker 14 (Fig. 1) . Similarly, the microphone input contact 30 is electrically connected to conventional microphone circuitry within the housing 12 which receives and processes an audio signal from the microphone 16 (Fig. 1) . The terminal 10 determines whether an accessory is connected to the connector 18 from a signal on the hook contact 34. The terminal 10 provides a serial digital data signal to the data output connector 36 and receives a serial digital data signal on the data input connector 36. A PTT controller 50 accessory according to one embodiment of the present invention is shown in Fig. 3. The PTT controller 50 includes a connector 52, a PTT handset 54, and a cable 56 which is electrically connected therebetween.

The connector 52 includes a connector housing 58, a pair of retaining posts 60 which extend outwardly from the housing 58, and 12 electrical spring contacts 62. The retaining posts 60 are aligned with the windows 42 (Fig. 2) of the connector 18 (Fig. 2) and the spring contacts 62 are aligned with the contacts 22 (Fig. 2) . Upon insertion of the retaining posts 60 into the windows 42 (Fig. 2), an electronic interface is formed between the spring contacts 62 and 22 (Fig. 2) which conducts electrical signals between the connector 18 (Fig. 2) and the PTT handset 54. The PTT handset 54 includes a housing 64 in which a depressable PTT switch 66, a speaker 68, a microphone 70, a volume control 72, and a call button 74 are disposed. The circuitry of the PTT handset 54, when the PTT controller 50 (Fig. 1) is electrically connected to the cellular terminal 10 (Fig. 1), is shown in Fig. 4. The hook contact 34 is tied to the power contact 24 to signal the connection of PTT controller 50 to the terminal 10.

Audio signals from the speaker output contact 28, of terminal 10 (Fig. 1), are selectively conducted through the PTT switch 66, variably attenuated by the volume control 72, shown as a variable resistor, amplified by an amplifier 80, and conducted to the speaker 68 where they are broadcast to the user. In this manner, the user can monitor a group call while the terminal 10 is remotely located from the user's ear, such as when the terminal 10 is connected to the user's waist belt. The user adjustably increases the volume of the audio signal, via the volume control 72, to compensate for noisy environments, such as along a road with passing cars, or to monitor a more remotely located terminal.

Audio signals which are received by the microphone 70 are amplified by an amplifier 82 and selectably conducted through the PTT switch 66 to the microphone input contact 30, of terminal 10 (Fig. 1) . The amplifiers, 80 and 82, receive power from the battery 20 (Fig. 1) through the power and ground contacts 24 and 26.

The PTT switch 66 is a conventional double-pole single-throw switch which is biased, such as by a spring (not shown) , to conduct the audio signal from the audio output connector 28 to the speaker 68, while electrically isolating the microphone 70 from the microphone input contact 30, when the PTT switch 66 is not depressed. Consequently, while the PTT switch 66 is not depressed, the microphone 70 is muted and the speaker 68 is connected to broadcast any group communications from the terminal 10 (Fig. 1) . In contrast, when the PTT switch 66 is depressed, the audio signal from the microphone 70 is conducted to the microphone input contact 30 while the speaker 68 is electrically isolated from the audio output connector 28 to mute the speaker and avoid feedback from the speaker 68 through the microphone 70.

Connected in parallel to the PTT switch 66 is a voice activated circuit 68 which provides similar mutually exclusive connectivity as the PTT switch 66. When the audio signal level from the microphone 70 is below a threshold amount, the voice activated circuit 68 conducts the audio signal from the audio output connector 28 to the speaker 68. In contrast, The voice activated circuit 68 responds to a signal level from the microphone 70 above a threshold amount by connecting the audio signal from the microphone 70 to the microphone input contact 30. In this manner, the PTT controller 50 (Fig. 3) provides half- duplex audio communications through the cellular terminal 10 (Fig. 1) . Consequently, users can monitor audio communications by other users within the group while the microphones, in terminals with which users are not depressing the PTT switches, are muted to minimize noise in the communicated signals. The user can signal the terminal 10 (Fig. 1) to establish a group call by momentarily depressing the call button 74 on the PTT handset 54 (Fig. 3) . The call button 74 is a conventional signal- pole single-throw switch which, when depressed, conducts the digital signal from the data output contact 36 to the data input contact 38 to signal the terminal 10 to establish a group call. Alternatively, the call button 74 can modify the digital signal which is conducted between the contacts 36 and 38, such as by inverting the digital signal with an invertor or shifting the phase or duty cycle of the digital signal with a conventional inductive- capacitive circuit, to signal the terminal 10.

The terminal 10 responds to the signaling on the data input contact 38 by calling a predetermined phone number. A base station and associated network switch can then assign a common voice channel, and time-slot for TDMA systems, to a predetermined group of other terminals which have been assigned the called phone number. Alternatively, the base station and associated network switch can respond to the called phone number by, in turn, calling a predetermined phone number for each of the terminals in the predetermined group and assigning a common voice channel, and time- slot for TDMA systems, to the grouped terminals. Instead of assigning a common voice channel to grouped terminals, the base station and associated network switch can assign different voice channels to each grouped terminal and distribute communications signals from each voice channel to the other voice channels. While the invention has been described in connection with what is presently considered to be the preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment, but to the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

Claims

What is claimed is:

1. An apparatus which provides half-duplex communications through a full-duplex mobile cellular terminal, the cellular terminal outputs a speaker signal and receives a microphone input signal, the apparatus comprising: a speaker for broadcasting the speaker signal to a user; a microphone which generates the microphone input signal; and a switch having a first operation state and a different second operation state, wherein when the switch is in the first operation state the speaker signal from the cellular terminal is electrically connected to the speaker and the microphone input signal from the microphone is substantially electrically isolated from the cellular terminal and when the switch is in the second operation state the microphone input signal from the microphone is electrically connected to the cellular terminal and the speaker is substantially electrically isolated from the speaker signal from the cellular terminal .

2. The apparatus according to claim 1, wherein the switch comprises : a mechanical switch which is movable between a first position to provide the first operation state and a different second position to provide the second operation state.

3. The apparatus according to claim 2, wherein: the mechanical switch is depressed to move from the first position to the second position.

4. The apparatus according to claim 1, wherein the switch comprises : a voice activated circuit which provides the first operation state when the microphone receives an audio signal level which is less than a predetermined threshold value and which provides the second operation state when the audio signal level is at least equal to the predetermined threshold value.

5. The apparatus according to claim 1, further comprising: an audio amplifier which is connected to the speaker and adjusts the magnitude of the speaker signal provided to the speaker in response to a user indication to change the speaker volume.

6. The apparatus according to claim 1, further comprising: a group call switch which, when actuated by the user, generates a group call signal, indicative of the user's desire to establish a group call, to the cellular terminal.

7. The apparatus according to claim 6 with the cellular terminal further providing a data output signal and a data input signal, wherein: the group call switch, when actuated by the user, connects the data output signal to the data input signal of the cellular terminal to indicate to the cellular terminal the user' s desire to establish a group call.

8. The apparatus according to claim 6 with the cellular terminal further providing a data output signal and a data input signal, wherein: the group call switch, when actuated by the user, modifies the data output signal conducted to the data input signal of the cellular terminal to indicate to the cellular terminal the user' s desire to establish a group call.

9. The apparatus according to claim 1, further comprising: a handset housing which is sufficiently small to be carried within a user's hand, wherein the speaker, the microphone, and the switch are disposed within the handset housing; and a signal conductive cable which is connected between the handset housing and the cellular terminal.

10. In an apparatus which includes a speaker and a microphone which are connected to a remotely located full-duplex mobile cellular terminal, a method for providing half-duplex communications through the full-duplex mobile cellular terminal, the method comprising the steps of: first conducting a speaker signal from the cellular terminal to the speaker for broadcast to a user while substantially preventing conduction of a microphone signal from the microphone to the cellular terminal; second conducting the microphone signal from the microphone to the cellular terminal while substantially preventing conduction of the speaker signal from the cellular terminal to the speaker; and transferring from the first conducting step to the second conducting step in response to the user indicating a desire to transmit an audio signal through the cellular terminal.

11. The method of claim 10, further comprising the step of: transferring from the first conducting step to the second conducting step in response to the microphone receiving an audio level which is at least as great as a threshold value.

12. The method of claim 10, further comprising the step of: adjusting the volume of the speaker signal broadcast to the user in response to the user indicating a desire to change the volume .

13. The method of claim 10, further comprising the step of: signaling the cellular terminal to call a predetermined number .

14. The method of claim 10, further comprising the step of: signaling the cellular terminal to establish a group call with a predetermined group of other cellular terminals.