Main station and substation in a network and a method for transmitting data in a network

A network station for a data network for receiving external data and for transmitting device-internally prepared data, comprising:

• a repeater for transmitting an external data packet received at a data input to a data output;
• a first data preparation unit for transmitting an internal data packet generated from the prepared data via the data output;
• a switching device for interrupting a data path between the data input and the data output;
• a control unit that is connected to the switching device in order, in a first operating mode, to block the transmission of the received external data packet via the data output if the internal data packet is currently being transmitted via the data output by the data preparation unit, and to permit the transmission of the received data packet by the repeater via the data output if no internal data packet is currently being transmitted via the first data preparation unit, wherein the control unit is configured so that it functions cyclically, in the first operating mode during a first time interval and in a second operating mode during a second time interval;
• further comprising a second data preparation unit for transmitting the prepared data;
• and the control unit is connected to the switching device in order, in the second operating mode, to connect the data output to the repeater and the second data preparation unit in alternating fashion so that a part of a particular data packet received at the data input is transmitted by the repeater to the data output and so that the prepared data are inserted into the data packet at a chronologically defined position of a defined data packet.