Multiplexing device capable of quickly transmitting a monitoring information

A network system comprising a main multiplexing device having a main address number which is assigned to said main multiplexing device, a subsidiary multiplexing device having a subsidiary address number and communicable with said main multiplexing device, and a monitoring device communicable with said main multiplexing device for monitoring said main and said subsidiary multiplexing devices, said main multiplexing device comprising a main receiving section for receiving a main transmitting section for transmitting a transmission signal to a main transmission line, said subsidiary multiplexing device comprising a subsidiary receiving section for transmission signal as a subsidiary reception signal through said transmission line and subsidiary transmitting section for transmitting a subsidiary transmission signal through a subsidiary transmission line,

• said monitoring device comprising:
• command supplying means for supplying said main multiplexing device with a command signal carrying a command and an address code;
• said main receiving section comprising:
• a reception terminal for receiving said command signal;
• detecting means responsive to said command signal for detecting whether or not said address code is coincident with said main address number to produce a detecting signal when said address code is coincident with said main address number, said detecting means producing a non-detection signal when said address code is not coincident with said main address number;
• and
• producing means responsive to said command carried by said command signal for generating a monitoring information signal indicative of a result of monitoring said main multiplexing device;
• said transmitting section comprising:
• information supplying means responsive to said detection signal for supplying said monitoring information signal to said monitoring device;
• and
• multiplexing means responsive to said non-detection signal for multiplexing said reception signal and said command signal into a multiplexed signal to transmit said multiplexed signal as said transmission signal to said transmission line;
• said subsidiary reception signal having a received signal frame and carrying said command signal in a predetermined area of said received signal frame;
• said subsidiary transmission signal having a transmitting signal frame and carrying a response signal, said transmitting signal frame being equivalent to said received signal frame;
• said subsidiary receiving section comprising:
• first detecting means responsive to said command signal for detecting whether or not said address code is coincident with said subsidiary address number to produce a subsidiary detection signal when said address is coincident with said subsidiary address number;
• second detecting means for detecting whether or not a vacant area exists in said received signal frame to produce a location signal representative of a location of said vacant area when said vacant area exists in said received signal frame;
• subsidiary producing means responsive to said command carried by said command signal for producing a subsidiary monitoring information signal indicative of a result of monitoring said subsidiary multiplexing device;
• and
• subsidiary supplying means responsive to said subsidiary detection signal for supplying said subsidiary monitoring information signal as said response signal to said subsidiary transmitting section;
• said subsidiary transmitting section comprising:
• entering means responsive to said location signal for transmitting signal frame to produce said subsidiary transmission signal carrying said response signal.