A communication apparatus which is capable of communicating based on a first communication system via a transmission channel, wherein another communication apparatus is communicating based on a second communication system via the transmission channel, comprising: an integrated circuit; a housing which is adapted for including the integrated circuit; a connector which is adapted for connecting the transmission channel provided on a rear plane of the housing; an indicator which is provided on a front plane of the housing; wherein the integrated circuit is characterized by comprising: a transmitter (11B1, 11B2, 31B, 42D) which is adapted for transmitting a first notice (ΦA) within a first notification domain in a first communication cycle; a detector (11B1, 11B2, 31B, 42D) which is adapted for detecting a second notice (ΦB) transmitted from the another communication apparatus within a second notification domain in a second communication cycle after the first communication cycle; wherein the transmitter (11B1, 11B2, 31B, 42D) is adapted for transmitting a data signal in a data transmission domain of the second communication cycle or a third communication cycle after the second communication cycle, wherein the data transmission domain is allocated to the first communication system on the basis of the first notice (ΦA) and the second notice (ΦB), wherein the rear plane is an opposite plane for the front plane. an integrated circuit; a housing which is adapted for including the integrated circuit; a connector which is adapted for connecting the transmission channel provided on a rear plane of the housing; an indicator which is provided on a front plane of the housing; wherein the integrated circuit is characterized by comprising: a transmitter (11B1, 11B2, 31B, 42D) which is adapted for transmitting a first notice (ΦA) within a first notification domain in a first communication cycle; a detector (11B1, 11B2, 31B, 42D) which is adapted for detecting a second notice (ΦB) transmitted from the another communication apparatus within a second notification domain in a second communication cycle after the first communication cycle; wherein the transmitter (11B1, 11B2, 31B, 42D) is adapted for transmitting a data signal in a data transmission domain of the second communication cycle or a third communication cycle after the second communication cycle, wherein the data transmission domain is allocated to the first communication system on the basis of the first notice (ΦA) and the second notice (ΦB), wherein the rear plane is an opposite plane for the front plane. a transmitter (11B1, 11B2, 31B, 42D) which is adapted for transmitting a first notice (ΦA) within a first notification domain in a first communication cycle; a detector (11B1, 11B2, 31B, 42D) which is adapted for detecting a second notice (ΦB) transmitted from the another communication apparatus within a second notification domain in a second communication cycle after the first communication cycle; wherein the transmitter (11B1, 11B2, 31B, 42D) is adapted for transmitting a data signal in a data transmission domain of the second communication cycle or a third communication cycle after the second communication cycle, wherein the data transmission domain is allocated to the first communication system on the basis of the first notice (ΦA) and the second notice (ΦB), wherein the rear plane is an opposite plane for the front plane.