Abstract: A telephone network access device switchable between a VOIP service and a PSTN service includes an RJ-11 port, a voice splitter, a first relay, a second relay, a SLIC chip, a CPU, and a ring detection unit. The ring detection unit outputs a first switch signal in response to detecting a ring signal of a PSTN communication. The second relay connects the telephone to the VOIP network in response to a power on event. The CPU controls the first relay and the second relay to connect the telephone to the PSTN network in response to the CPU receiving the first switch signal, and controls the second relay to reconnect the telephone to the VOIP network when the PSTN communication ends.

Abstract: A telephone network access device switchable between a VOIP service and a PSTN service includes an Rj-11 port, a voice splitter, a first relay, a second relay, a SLIC chip, a CPU, and a ring detection unit. The ring detection unit outputs a first switch signal in response to detecting a ring signal of a PSTN communication. The second relay connects the telephone to the VOIP network in response to a power on event. The CPU controls the first relay and the second relay to connect the telephone to the PSTN network in response to the CPU receiving the first switch signal, and controls the second relay to reconnect the telephone to the VOIP network when the PSTN communication ends.

Abstract: A communication device electronically connects with a phone and includes a control unit, a relay, a public switched telephone network (PSTN) interface, a voice over Internet Protocol (VoIP) network interface, and a ring signal detector. The relay is electronically connected with the control unit. The PSTN interface and the VoIP interface are electronically connected with the relay. The ring signal detector is electronically connected with the control unit and the PSTN interface. The control unit controls the relay to connect the phone with the PSTN interface when the ring signal detector detects a PSTN ring signal. In one embodiment, the control unit controls the relay to connect the phone with the VoIP interface.

Abstract: An inrush current limitation circuit for limiting inrush current when powered-on includes a power source, a switch, a voltage dividing circuit, a second diode, a transistor, a zener diode, a charging capacitor and a first diode. The voltage dividing circuit is connected between a second end of switch and a ground to divide the direct current voltage to obtain a trigger voltage signal. An anode of the second diode is connected to the second end of the switch. A base of the transistor electrically is connected to a cathode of the second diode, and a collector connected to the cathode of the second diode. A cathode of the zener diode is connected to the base of the transistor; an anode of the zener diode is connected to the ground.