Patent Publication Number: US-2012027009-A1

Title: Communication device and method thereof

Description:
BACKGROUND 
     1. Technical Field 
     The present disclosure relates to a communication device capable of automatically connecting a phone to different communication networks. 
     2. Description of Related Art 
     Integrated access devices (IADs) are popularly used for connecting a phone to different communication networks. The IADs include a voice over Internet Protocol (VoIP) interface and a public switch telephone network (PSTN) interface. A phone cable of the phone is manually connected with the VoIP interface for VoIP communication requirements, and is manually connected with the PSTN interface for PSTN communication requirements. The requirements for such manual connections are inconvenient. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram of one embodiment of a communication device. 
         FIG. 2  is a block diagram of one embodiment of a ring signal detector of  FIG. 1 . 
         FIG. 3  is a flowchart illustrating one embodiment of a method for automatically connecting a phone to different communication networks. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  is a block diagram of one embodiment of a communication device  100 . The communication device  100  is capable of connecting a phone  400  to a public switch telephone network (PSTN)  200  and a voice over Internet Protocol (VoIP) network  300 . The communication device  100  includes a PSTN interface  10 , a VoIP interface  20 , a ring signal detector  30 , a relay  40 , and a control unit  50 . In the embodiment, the communication device  100  is an integrated access device (IAD). 
     The PSTN interface  10  is configured to communicate with the PSTN  200  and is electronically connected with the relay  40 . The VoIP interface  20  is configured to communicate with the VoIP network  300  and is electronically connected with the relay  40 . The ring signal detector  30  is configured to detect a PSTN ring signal from the PSTN  200 , and is electronically connected with the PSTN interface  10  and the control unit  50 . The relay  40  is electronically connected with the control unit  50 . 
       FIG. 2  is a block diagram of one embodiment of the ring signal detector  30  of  FIG. 1 . The ring signal detector  30  includes a positive wire Tip, a negative wire Ring, a bridge rectifier  32 , a protection circuit  34 , a Zener diode ZD, and a trigger circuit  36 . The positive wire Tip and the negative wire Ring are both electronically connected with the PSTN interface  10  and the bridge rectifier  32 , and configured to receive the PSTN ring signal. The bridge rectifier  32  includes two input terminals  322 , an output terminal  324 , and a ground terminal  326 . The two input terminals  322  are individually electronically connected with the positive wire Tip and the negative wire Ring, and configured to receive the PSTN ring signal. The bridge rectifier  32  may transform the PSTN ring signal into a direct current (DC) signal and output the DC signal through the output terminal  324 . The ground terminal  326  is connected to ground. 
     The protection circuit  34  includes a varistor  342 , a first resistor R 1 , a second resistor R 2 , and a capacitor  348 . The varistor  342  is electronically connected with the output terminal  324  and the ground terminal  326  of the bridge rectifier  32 . When the ring signal detector  30  receives a surge voltage, the varistor  342  may generate a short circuit to protect the ring signal detector  30 . The first resistor R 1  and the second resistor R 2  are used to provide current limiting for the PSTN ring signal. The first resistor R 1  is electronically connected in series with the second resistor R 2 , and is electronically connected with the varistor  342  and the output terminal  324 . 
     The capacitor  348  is used for filtering. One terminal of the capacitor  348  is electronically connected between the first resistor R 1  and the second resistor R 2 , and other terminal of the capacitor  348  is connected to ground. The Zener diode ZD and the capacitor  348  are electronically connected in parallel. A negative terminal of the Zener diode ZD is electronically connected with the second resistor R 2 , and a positive terminal of the Zener diode ZD is connected to ground. When the voltage of the PSTN ring signal exceeds a breakdown voltage of the Zener diode ZD, the Zener diode ZD is in a reverse breakdown state. As a result, voltages of two terminals of the Zener diode ZD remain constant to stabilize the voltage of the PSTN ring signal. 
     The trigger circuit includes a bias resistor R, a field-effect transistor (FET) Q, a power supply P, a third resistor R 3 , and a fourth resistor R 4 . The bias resistor R is electronically connected in parallel with the Zener diode ZD, and provides the FET Q with a bias voltage. The FET Q includes a gate terminal G, a source terminal S, and a drain terminal D. The gate terminal G, the bias resistor R, and the negative terminal of the Zener diode ZD are electronically connected together. The source terminal S is connected to ground. The drain terminal D is individually electronically connected with the power supply P and the control unit  50  through the third resistor R 3  and the fourth resistor R 4 . 
     The voltage of the power supply P can be 3.3V, for example. The fourth resistor R 4  is configured to prevent the control unit  50  from being damaged by large currents. When the PSTN ring signal flows through the Zener diode ZD, the Zener diode ZD is in a reverse breakdown state and the voltage of the Zener diode ZD remains substantially constant. As a result, the voltage of the gate terminal G exceeds the voltage of the source terminal S, and the FET Q is turned on. After the FET Q is turned on, the current flows from the drain terminal D to the source terminal S, and therefore the voltage of the drain terminal D decreases. The voltage of the drain terminal D during the FET Q is turned on is a low electric potential signal relative to that during the FET Q is turned off. The FET Q is turned off when no PSTN ring signal is received. The voltage of the drain terminal D during the FET Q is turned off is a high electric potential signal relative to that during the FET Q is turned on. 
     The relay  40  includes connection terminals A 1 -A 6 . The connection terminals A 1  and A 2  are electronically connected with the phone  400  through a voice interface (not shown). The connection terminals A 3  and A 4  are electronically connected with the PSTN interface  10 . The connection terminals A 5  and A 6  are electronically connected with the VoIP interface  20 . 
     The control unit  50  may be a central processing unit (CPU) of the communication device  100 , and is electronically connected with the relay  40 . The control unit  50  may detect the voltage of the drain terminal D and control the relay  40  based on the voltage of the drain terminal D. When detecting the low electric potential signal outputted from the drain terminal D, the control unit  50  connects the connection terminals A 1  and A 2  with the connection terminals A 3  and A 4 . The phone  400  may be connected to the PSTN  200 . When detecting the high electric potential signal outputted from the drain terminal D, the control unit  50  connects the connection terminals A 1  and A 2  with the connection terminals A 5  and A 6 . The phone  400  may be connected to the VoIP network  300 . 
       FIG. 3  is a flowchart illustrating one embodiment of a method for automatically connecting the phone  400  to different communication networks. Depending on the embodiment, additional blocks may be added, others removed, and the ordering of the blocks may be changed. 
     In block S 1 , the ring signal detector  30  determines whether the PSTN ring signal is received. If no PSTN ring signal is received, in block S 2 , the control unit  50  control the relay  40  to connect the phone  400  to the VoIP network  300 . 
     If the PSTN ring signal is received, in block S 3 , the ring signal detector  30  triggers the low electric potential signal and transmits the low electric potential signal to the control unit  50 . 
     In block S 4 , the control unit  50  controls the relay  40  to connect the phone  400  to the PSTN  200 . 
     In block S 5 , the ring signal detector  30  triggers the high electric potential signal and transmits the high electric potential signal to the control unit  50  when the PSTN ring signal ends. 
     In block S 6 , the control unit  50  control the relay  40  to connect the phone  400  to the VoIP network  300 , and block S 1  is repeated. 
     The present disclosure provides a communication device to automatically connect a phone to a PSTN or a VoIP network for different requirements. Manual switching between the PSTN and the VoIP network for the phone may be avoided. 
     Although certain inventive embodiments of the present disclosure have been specifically described, the present disclosure is not to be construed as being limited thereto. Various changes or modifications may be made to the present disclosure without departing from the scope and spirit of the present disclosure.