Network terminal, method for controlling the same, and network system

A network system comprising

• a plurality of network terminals which perform communication through the transmission path, each of the network terminals including:
• an oscillator circuit which generates a clock;
• a communication processing unit configured to transmit and receive communication data through the transmission path, using the clock;
• a controller unit configured to control a function of the network terminal, using the clock;
• a clock control unit configured to cause the oscillator circuit to start or stop oscillating, and supply the clock generated by the oscillator circuit to the communication processing unit and the controller unit;
• and
• a signal detecting unit configured to monitor a wave detection signal communicated through the transmission path in a case where the communication processing unit is not operating, and generate an activation signal according to which the clock control unit causes the oscillator circuit to start oscillating at a time when the wave detection signal exceeds a threshold value,
• wherein the signal detecting unit is configured with a circuit operable without using the clock, and
• the controller unit is configured to switch a wave detection signal detectable by the signal detecting unit, by changing a circuit constant of the signal detecting unit, and
• at least one of the plurality of network terminals further including:
• an activation signal control unit configured to generate the activation signal independently,
• wherein the activation signal control unit:
• includes one of an external interrupt circuit, a timer, a serial interface, and a sensor IF circuit;
• and
• is configured to generate the activation signal triggered by one of an input signal from an external device, an end of a count by the timer, an ambient temperature, and a vibration,
• the communication processing unit is configured to transmit, through a transmission path, a wave detection signal to other network terminals connected through the transmission path, and
• the controller unit is configured to cause the communication processing unit to transmit the wave detection signal which is detectable by a particular one of the other network terminals, by changing a waveform or a frequency of the detection signal transmitted by the communication processing unit.

A method of controlling a network terminal including an oscillator circuit which generates a clock and communicates through a transmission path, the method comprising:

• transmitting and receiving communication data through the transmission path, using the clock;
• controlling a function of the network terminal, using the clock;
• causing the oscillator circuit to start or stop oscillating, and supplying the clock generated by the oscillator circuit;
• and
• monitoring a wave detection signal communicated through the transmission path in a case where the communication processing unit is not operating, and generating an activation signal according to which the oscillator circuit is caused to start oscillation at a time when the wave detection signal exceeds a threshold value,
• wherein the monitoring can be performed without using the clock, and
• in the controlling, a switch of a wave detection signal detectable in the monitoring is performed, by changing a circuit constant as a function of the network terminal.