Telecommunications – Transmitter and receiver at separate stations – Single message via plural carrier wave transmission
Reexamination Certificate
1998-08-27
2001-01-30
Hunter, Daniel S. (Department: 2744)
Telecommunications
Transmitter and receiver at separate stations
Single message via plural carrier wave transmission
C455S574000, C455S088000, C455S063300, C320S124000
Reexamination Certificate
active
06181916
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a communication system, and more particularly to a communication system having a primary unit and a secondary unit.
BACKGROUND OF THE INVENTION
The radio (or wireless) telephone having separable base and handset is extensively used since the user is free from being unnecessarily unduly confined to a reletively limited space. In use, the handset, however, will be noised when:
1) The handset is out of range;
2) The base has a power failure or an interrupted power; or
3) There exists a noise source.
As shown in
FIG. 1
, there is shown a conventional radio telephone in which the base includes a power-stabilizing circuit
11
, a digital controller or central processing unit (CPU)
12
, a radio frequency transmitting module
13
including a transmitting driver
131
and a transmitting amplifier
132
, a transmission signal processor
24
, a transmission data processor
25
, a receiving data processor
26
, a receiving signal processor
27
and a receiver
28
. Likewise, the handset includes a receiver
14
, a receiving signal processor
15
, an amplifier
16
, a speaker
17
, an antenna
18
, a receiving data processor
19
, a transmitting amplifier
20
, a transmitting driver
21
, a transmission signal processor
22
, a transmission data processor
23
, a digital controller or CPU
191
, a display
192
and a keypad
193
.
Upon power failure or interruption of the base, there is no signal transmitted from radio frequency transmitting module
13
. Nevertheless, the handset is still powered on which means that receiver
14
, receiving signal processor
15
and audio amplifier
16
are still in a working mode through which any signal including a noise can transmit to speaker
17
which will sound to the user only the unpleasant amplified noise since the carrier wave has disappeared through the power failure or interruption of the base. As described above, there are three noise sources. The user will be bothered to inevitably try to redial the telephone in vain if he or she is not able to quickly get alert to the fact the base is suffering from a power failure or interruption.
It is therefore tried by the applicant to deal with the above situation, i.e. the base has a power failure or an interrupted power, encountered by the prior art.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a communication system being user friendly.
It is further an object of the present invention to provide a communication system capable of freeing the manufacturer from being mistakenly by the user as a poor product source.
It is another object of the present invention to provide a mode-changing method for a communication system.
According to the present invention, a communication system includes a primary unit transmitting a first signal at a first instance, receiving a second signal at a second instance and energized by a power source having a voltage level, a secondary unit transmitting a third signal at a first instance, receiving a fourth signal at a second instance, and having a first communication mode and a second communication-shut mode, and a mode-changing device electrically connected to the primary unit and enabling the primary unit to generate a mode-changing signal to be received by the secondary unit for changing the secondary unit from the first communication mode into the second communication-shut mode when the voltage level falls below a specific value.
Preferably the mode-changing device includes a power detector electrically connected to the power source for detecting the voltage level, and outputs a first voltage when the voltage level is higher than the specific value and a second voltage when the voltage level is lower than the specific value. Certainly, the first voltage can be a working voltage of the primary unit and the second voltage can be 0.
Preferably the mode-changing device further includes a timer which begins to count a time period during which the voltage level is kept below the specific value so that a surging phenomenon can be avoided. Certainly, the primary unit can transmit the mode-changing signal to the secondary unit when the timer has counted up the time period.
Normally, the primary unit further includes a digital controller or CPU in which the timer is built.
Preferably the secondary unit further includes a display for displaying the secondary unit is in the communication-shut mode in which the noise cannot be heard and the secondary unit is uncommunicable.
Certainly, the primary unit can be a base of a radio telephone and the secondary unit can be a handset of the radio telephone.
According to another aspect of the present invention, a mode-changing method for a communication system including a primary unit transmitting a first signal at a first instance, receiving a second signal at a second instance and adapted to be energized by a power source having a voltage level, and a secondary unit transmitting a third signal at a first instance, receiving a fourth signal at a second instance and having a first communication mode and a second communication-shut mode includes the following steps of a) detecting said voltage level, b) generating a mode-changing signal when the voltage level falls below a specific value, and c) changing the secondary unit from the first communication mode into the second communication-shut mode in response to the mode-changing signal.
The present invention may best be understood through the following descriptions with reference to the accompanying drawings, in which:
REFERENCES:
patent: 5111499 (1992-05-01), Umemoto et al.
patent: 5363430 (1994-11-01), Yamagata et al.
patent: 5426690 (1995-06-01), Hikuma et al.
patent: 5867798 (1999-02-01), Inukai et al.
Chen Chung Chang
Mou Michael
Dbtel Incorporated
Gantt Alan T.
Hunter Daniel S.
Rosenberg , Klein & Lee
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