Transmitting/receiving device (12; 32) for a subscriber station (10; 30) of a serial bus system , having a first connection for receiving a transmission signal (TxD) from a communication control device (11; 31), a transmitter for transmitting the transmission signal (TxD) onto a bus of the bus system , in which bus system at least one first communication phase and a second communication phase are used to interchange messages (45; 46) between subscriber stations of the bus system , a receiver for receiving the signal from the bus , wherein the receiver is configured to generate a digital reception signal (RxD) from the signal received from the bus , and a second connection for transmitting the digital reception signal (RxD) to the communication control device (11; 31) and for receiving an additional signal (RxD_TC) from the communication control device (11; 31), characterized by an operating mode switching block (15; 35) for evaluating the reception signal (S_SW) output by the receiver and a signal (RxD_TC) received at the second connection from the communication control device (11; 31), wherein the operating mode switching block (15; 35) is configured to switch the transmitter and/or the receiver into one of at least two different operating modes on the basis of a result of the evaluation and to switch at least one predetermined operating mode of the operating modes to another of the operating modes after expiry of a period of time (T0) which can be preset in the operating mode switching block (15; 35) for additional internal communication between the communication control device (11; 31) and the transmitting/receiving device (12; 32) via the second connection. a first connection for receiving a transmission signal (TxD) from a communication control device (11; 31), a transmitter for transmitting the transmission signal (TxD) onto a bus of the bus system , in which bus system at least one first communication phase and a second communication phase are used to interchange messages (45; 46) between subscriber stations of the bus system , a receiver for receiving the signal from the bus , wherein the receiver is configured to generate a digital reception signal (RxD) from the signal received from the bus , and a second connection for transmitting the digital reception signal (RxD) to the communication control device (11; 31) and for receiving an additional signal (RxD_TC) from the communication control device (11; 31), characterized by an operating mode switching block (15; 35) for evaluating the reception signal (S_SW) output by the receiver and a signal (RxD_TC) received at the second connection from the communication control device (11; 31), wherein the operating mode switching block (15; 35) is configured to switch the transmitter and/or the receiver into one of at least two different operating modes on the basis of a result of the evaluation and to switch at least one predetermined operating mode of the operating modes to another of the operating modes after expiry of a period of time (T0) which can be preset in the operating mode switching block (15; 35) for additional internal communication between the communication control device (11; 31) and the transmitting/receiving device (12; 32) via the second connection. <EOS>