Two-way communication system, and delay and transmission level methods

A two-way communication system comprising:

• a center station;
• subscriber stations each for mutually exchanging signals with said center station;
• a relay station for relaying signals between said center station and said subscriber stations;
• a relay transmission line connected between said center station and said relay station and duplex systematized by a working system and a stand-by system;
• and
• a subscriber transmission line connected between said relay station and said subscriber stations,
• wherein said center station measures a round-trip propagation delay when a subscriber station starts its operation and then sets a transmission delay of said subscriber station so as to equalize the round-trip propagation delay measured to said subscriber station to a fixed system delay;
• wherein said center station measures a round-trip propagation delay of a signal to said relay station when said relay station starts its operation;
• and
• wherein when a link switching operation from said working system to said stand-by system occurs due to a failure of said relay transmission line or when a link switching operation from said stand-by system to said working system occurs due to a recovery of a failed relay transmission line, said center station measures a round-trip propagation delay of a signal to said relay station after the link switching operation and then resets transmission delays of all subscriber stations connected to said relay station based on a difference between said measured delay and a round-trip propagation delay to a signal to said relay station before the link switching operation.

A two-way communication system comprising:

• a center station;
• subscriber stations each for mutually exchanging signals with said center station;
• a relay station for relaying signals between said center station and said subscriber stations;
• a relay transmission line connected between said center station and said relay station and duplex systematized by a working system and a stand-by system;
• and
• a subscriber transmission line connected between said relay station and said subscriber stations,
• wherein said center station measures a receive level when a subscriber station starts its operation and then sets the transmission level of said subscriber station so as to equalize the receive level measured to said subscriber station to a fixed system receive level;
• and
• wherein when a link switching operation from said working system to said stand-by system occurs due to a failure of said relay transmission line or when a link switching operation from said stand-by system to said working system occurs due to a recovery of a failed relay transmission line, said center station resets transmission level set values of all subscriber stations connected to said relay station based on a difference between the measured receive level and a receive level of a signal to a subscriber station after the link switching operation.

A two-way communication system comprising:

• a center station;
• subscriber stations each for mutually exchanging signals with said center station;
• a relay station for relaying signals between said center station and said subscriber stations;
• a relay transmission line connected between said center station and said relay station and duplex systematized by a working system and a stand-by system;
• and
• a subscriber transmission line connected between said relay station and said subscriber stations,
• wherein said center station measures a receive level when a subscriber station starts its operation and then sets the transmission level of said subscriber station so as to equalize the receive level measured to said subscriber station to a fixed system receive level;
• wherein said center station measures a receive level of a signal to said relay station when said relay station starts its operation;
• and
• wherein when a link switching operation from said working system to said stand-by system occurs due to a failure of said relay transmission line or when a link switching operation from said stand-by system to said working system occurs due to a recovery of a failed relay transmission line, said center station measures a receive level of a signal to the relay station after said link switching operation and then resets transmission level set values of all subscriber stations connected to said relay station based on a difference between the measured receive level and a receive level of a signal to the subscriber station after the link switching operation.

A method of setting a delay in a center station comprising the steps of:

• measuring a round-trip propagation delay when a subscriber station starts its operation and then sets a transmission delay of said subscriber station so as to equalize the round-trip propagation delay measured to said subscriber station to a fixed system delay;
• measuring a round-trip propagation delay of a subscriber station after a link switching operation when a link switching operation from a working system to a stand-by system occurs due to a failure in a relay transmission line;
• and
• resetting transmission delays of all subscriber stations connected to said relay station based on a difference between the measured delay and a round-trip propagation delay of a signal to said subscriber station before said link switching operation.

A method of setting a delay in a center station comprising the steps of:

• measuring a round-trip propagation delay when a subscriber station starts its operation and then sets a transmission delay of said subscriber station so as to equalize the round-trip propagation delay measured to said subscriber station to a fixed system delay;
• measuring a round-trip propagation delay of a signal to a relay station when said relay station starts its operation;
• measuring a round-trip propagation delay of a signal to said relay station after the link switching operation when a link switching operation from a working system to a stand-by system occurs due to a failure of a relay transmission line or when a link switching operation from a stand-by system to said working system occurs due to a recovery of a failed relay transmission line;
• and
• then resetting transmission delays of all subscriber stations connected to said relay station based on a difference said measured delay and a round-trip propagation delay to a signal to said relay station before the link switching operation.

A method of setting a transmission level in a center station comprising the steps of:

• measuring a receive level when a subscriber station starts its operation;
• setting the transmission level of said subscriber station so as to equalize the receive level measured to said subscriber station to a fixed system receive level;
• and
• resetting transmission level set values of all subscriber stations connected to said relay station based on a difference between the measured receive level and a receive level of a signal to a subscriber station after the link switching operation when a link switching operation from a working system to a stand-by system occurs due to a failure of a relay transmission line or when a link switching operation from said stand-by system to said working system occurs due to a recovery of a failed relay transmission line.

A method of setting a transmission level in a center station comprising the steps of:

• measuring a receive level when a subscriber station starts its operation;
• setting the transmission level of said subscriber station so as to equalize the receive level measured to said subscriber station to a fixed system receive level;
• measuring a receive level of a signal to a relay station after said link switching operation when a link switching operation from a working system to a stand-by system occurs due to a failure of a relay transmission line or when a link switching operation from said stand-by system to said working system occurs due to a recovery of a failed relay transmission line;
• and
• then resetting transmission level set values of all subscriber stations connected to said relay station based on a difference between the measured receive level and a receive level of a signal to the subscriber station after the link switching operation.