Communications: electrical – Condition responsive indicating system – With particular coupling link
Reexamination Certificate
2003-04-22
2004-11-09
Goins, Davetta W. (Department: 2632)
Communications: electrical
Condition responsive indicating system
With particular coupling link
C340S539100, C340S539150, C340S539230, C340S870030, C340S870030, C455S090200, C455S134000, C455S421000
Reexamination Certificate
active
06816070
ABSTRACT:
BACKGROUND OF INVENTION
1. Field of the Invention
The present invention relates to a method of generating an alert for a walkie-talkie, more specifically, a method used in the walkie-talkie for generating a warning signal when the walkie-talkie will be out of communicable distance.
2. Description of the Prior Art
A continuous tone-coded squelch system (CTCSS) has been widely applied to wireless transmission, and is used to let a plurality of users communicate with each other within a predetermined communication area. The CTCSS adopts a low-frequency CTCSS tone signal to distinguish signals transmitted via the same physical channel. For instance, a prior art walkie-talkie utilizes the CTCSS to achieve group communication. Please refer to
FIG. 1
, which is a schematic diagram showing frequency bands used by the prior art CTCSS. As shown in
FIG. 1
, a band ranging from 62.5 Hz to 250 Hz is used to transmit the above-mentioned low-frequency CTCSS tone signal, and another band ranging from 300 Hz to 3.4 KHz is used to transmit speech signals spoken by a user. The operation of the CTCSS is described as follows. With regard to the prior art walkie-talkie, 14 channels P
1
-P
14
generally are adopted to carry signals, and the 14 channels are physical channels. In addition, 38 CTCSS tone signals T
1
-T
38
individually corresponding to different frequencies are used. One of the 38 CTCSS tone signals T
1
-T
38
annexed to one physical channel generates a specific logical channel, and the 14 physical channels are capable of forming
532
(14*38) logical channels in total. When a speaker sets the walkie-talkie with a physical channel P
1
and a desired CTCSS tone signal T
1
, that is, the logical channel set by the speaker becomes P
1
(T
1
). After the speaker presses a push-to-talk (PTT) button on the walkie-talkie, the speaker is capable of outputting speech signals via the walkie-talkie toward the predetermined communication area specified by the walkie-talkie. If there are three listeners in the predetermined communication area, and the three listener set their own logical channels as P
1
(T
1
), P
1
(T
38
), P
2
(T
1
) respectively. For the first listener with a logical channel P
1
(T
1
), because his walkie-talkie receives and transmits signals through the physical channel P
1
, the walkie-talkie of the first listener will start receiving speech signals spoken by the speaker. In addition, the walkie-talkie of the first listener judges that the CTCSS tone signal used by the speaker is T
1
. In other words, the speaker and the first listener both adopt the same logical channel P
1
(T
1
). Therefore, the walkie-talkie of the first listener then outputs the received speech signals via an audio speaker. The first listener is capable of hearing the speech signals spoken by the speaker. For the second listener with a logical channel P
1
(T
38
), because his walkie-talkie receives and transmits signals through the physical channel P
1
, the walkie-talkie of the second listener will start receiving speech signals spoken by the speaker. However, the walkie-talkie of the second listener judges that the CTCSS tone signal used by the speaker is not T
1
, but T
38
. In other words, the speaker and the second listener adopt different logical channels P
1
(T
1
) and P
1
(T
38
). Therefore, the walkie-talkie of the second listener then does not output the received speech signals via an audio speaker. The second listener cannot hear the speech signals spoken by the speaker. For the third listener with a logical channel P
2
(T
1
), because his walkie-talkie receives and transmits signals through the physical channel P
2
, the walkie-talkie of the third listener and that of the speaker use different physical channels. With the unmatched physical channel, the walkie-talkie of the third listener cannot acknowledge an adequate signal strength indicated by a received signal strength indicator (RSSI). Therefore, the walkie-talkie of the third listener will not receive any speech signals spoken by the speaker. That is, no speech signal is played by an audio speaker of the walkie-talkie. The second and third listeners cannot hear any speech signals spoken by the speaker, that is, the walkie-talkies of the second and third listeners both detect the CTCSS tone signal related to the received speech signals for actuating a signal squelch function. To sum up, only the users using the same logical channel can communicate with each other to achieve group communication.
Please refer to
FIG. 2
, which is a block diagram of a prior art walkie-talkie
10
. The walkie-talkie
10
has an antenna
11
, a transceiver
12
, a selector
14
, a processor
16
, a speaker
17
, a microphone
18
, and a speech signal processor
20
. The walkie-talkie
10
can receive and transmit radio frequency (RF) signals through the antenna
11
. With regard to receiving RF signals, the transceiver
12
converts the high-frequency RF signal into a low-frequency baseband signal Rx, and transmits the baseband signal Rx to the selector
14
. The selector
14
then outputs the baseband signal Rx from an output port A. The processor
16
determines frequency of a CTCSS tone signal according to the received baseband signal Rx. Generally speaking, the processor
16
has a low-pass filter (LPF) for extracting signals with frequencies ranging from 62.5 Hz to 250 Hz, and then the processor
16
judges the CTCSS tone signal related to the baseband signal Rx to decide whether the walkie-talkie
10
and the baseband signal Rx use the same logical channel. If the walkie-talkie
10
and the baseband signal Rx use the same logical channel, the processor
16
activates the speaker
17
to proceed following signal output operation. That is, the speech signal processor
20
has two analog filter circuits for extracting signals with frequencies ranging from 300 Hz to 3.4 KHz, and the extracted signals are played by the speaker
17
. On the contrary, if the walkie-talkie
10
and the baseband signal Rx use different logical channels, the processor
16
does not actuate the speech signal processor
20
and the speaker
17
. The walkie-talkie
10
, therefore, does not output any speech signals transmitted by unmatched logical channels. With regard to transmitting RF signals, when the user presses the PTT button, the selector
14
will chose the input port B, and the processor
16
simultaneously actuates the microphone
18
. Therefore, the speech signals spoken by the user are inputted into the speech signal processor
20
. As mentioned above, the speech signal processor
20
uses filter circuits to extract signals with frequencies ranging from 300 Hz to 3.4 KHz, and the speech signal processor
20
outputs the extracted signals to the CTCSS encoder
18
. Based on a CTCSS code (CTCSS tone signal with a specific frequency) set in the walkie-talkie
10
, the processor
16
adds a corresponding CTCSS tone signal in the extracted signals outputted from the speech signal processor
20
for forming a baseband signal Tx. In the end, the transceiver
12
converts the low-frequency baseband signal Tx into a high-frequency RF signal, and the RF signal is then outputted via the antenna
11
.
Generally speaking, because the radio signal easily is obstructed by obstacles, such as trees, thick leaf and building, or particle, such as steam and dust, which can limit the conversationscope for the walkie-talkie. As for the user, although the common walkie talkies are given a recommend conversation scope, but these scopes are estimation values. Under different environments, in fact, the really conversation scopes are not fixed, meaning that the user cannot know the real conversation scopes with each other. Therefore, unconsciously, a bad communication quality is caused by terrain and environmental factor.
SUMMARY OF INVENTION
It is therefore a primary objective of the claimed invention to provide a method used in a walkie-talkie for generating a warning signal while leaving a conversation distance to solve the aforementioned problem.
Briefly summarized, the claimed inve
Chen Ming-Hui
Hsu Jany-Yee
Conwise Technology Corporation Ltd.
Goins Davetta W.
Hsu Winston
LandOfFree
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