Ethernet fail-safe relay

A passive Ethernet by-pass switch comprising:

• a first connection configured to be coupled to a first Ethernet port;
• a second connection configured to be coupled to a second Ethernet port;
• switching circuitry including at least one internal switch operable to allow network communication between the first connection, the second connection, and at least one Ethernet controller,
• the at least one internal switch including a depletion mode transistor operable to bridge the first connection to the second connection to establish communication between the first connection and the second connection;
• and
• a first depletion mode transistor and a second depletion mode transistor,
• the first depletion mode transistor including a source connection and a gate connection,
• the second depletion mode transistor including a source connection and a gate connection,
• the source connection of the first depletion mode transistor coupled to the source connection of the second depletion mode transistor, and
• the gate connection of the first depletion mode transistor coupled to the gate connection of the second depletion mode transistor.

A system comprising:

• a first Ethernet port;
• a second Ethernet port;
• at least one Ethernet controller;
• at least one passive Ethernet by-pass switch comprising a first connection configured to be coupled to the first Ethernet port, a second connection configured to be coupled to the second Ethernet port, and switching circuitry including at least one internal switch operable to allow network communication between the first connection, the second connection, and the at least one Ethernet controller,
• the at least one internal switch including a depletion mode transistor operable to bridge the first connection to the second connection establish communication between the first connection and the second connection;
• and
• a first network device, a second network device, and a third network device, the second network device including the at least one passive Ethernet by-pass switch and configured to allow network communication between the first network device and the third network device responsive to the depletion mode transistor bridging the first connection to the second connection to maintain communication between the first connection and the second connection.

A method for bridging a node using a passive Ethernet by-pass switch, the passive Ethernet by-pass switch including a first connection, a second connection, and switching circuitry including at least one internal switch, the at least one internal switch including a depletion mode transistor, the method comprising:

• coupling the first connection to a first Ethernet port;
• coupling the second connection to a second Ethernet port;
• operating the at least one internal switch of the switching circuitry to allow network communication between the first connection, the second connection, and at least one Ethernet controller;
• operating a watchdog circuit to monitor a heartbeat signal from the at least one Ethernet controller;
• providing a signal indicative of the presence or absence of the heartbeat signal to a power monitoring circuit;
• responsive to receiving the signal during a time when the signal indicates the absence of the heartbeat signal, operating the Ethernet by-pass switch to cease providing power to the depletion mode transistor;
• and
• responsive to operating the Ethernet by-pass switch to cease providing power to the depletion mode transistor, bridging the first connection to the second connection via the depletion mode transistor to establish communication between the first connection and the second connection.

A method for bridging a node using a passive Ethernet by-pass switch, the passive Ethernet by-pass switch including a first connection coupled to a first Ethernet port, a second connection coupled to a second Ethernet port, switching circuitry including at least one internal switch operable to allow network communication between the first connection and the second connection, the at least one internal switch including a first depletion mode transistor and a second depletion mode transistor coupled source-to-source to each other, the method comprising:

• providing a voltage to a gate connection of the first depletion mode transistor;
• providing the voltage to a gate connection of the second depletion mode transistor;
• responsive to at least one of the first Ethernet port or the second Ethernet port losing power, ceasing to provide the voltage to the gate connection of the first depletion mode transistor and the second depletion mode transistor;
• and
• responsive to ceasing to provide the voltage, establishing communicative coupling between the first connection and the second connection.

A method for bridging a node to establish network communication between a first network device, via a second network device, to a third network device, the method comprising:

• coupling a first Ethernet port of the second network device to a respective Ethernet port of the first network device;
• coupling a second Ethernet port of the second network device to a respective Ethernet port of the third network device;
• communicatively coupling the first Ethernet port and the second Ethernet port to an Ethernet controller;
• determining that the Ethernet controller has lost power;
• and
• responsive to determining that the Ethernet controller has lost power, operating an Ethernet by-pass switch situated in the second network device to selectively couple the first Ethernet port to the second Ethernet port via at least one depletion mode transistor.