as a bit error occurred the control unit 2 will recognize the error due to the odd parity of the data in such a case the programming unit 2 will provide a 34 repeat 34 command to the programming unit 1 which then will repeat the last data transmitted if after several attempts the data still have not been transmitted correctly the programming unit 1 will terminate the transmission release the programming voltage on the release and enable bus 13 and will provide an output indication to the operator of 34 malfunction 34 for example by lighting a 34 malfunction 34 indicator mi the programming unit 1 can be so constructed that an error output listing can be printed out so that the data which are to be transmitted from the programming unit and stored in the memory 25 can be analyzed for errors so that specific error criteria can be targeted and then corrected the programming steps described are one of many possible steps they will depend specifically on the structure of data and respectively on the way the 34 handshake 34 between the programming unit 1 and the control unit 2 is carried out this will depend on the particular product specifications to be handled it is also possible to carry out synchronous serial data transmission over the lines 11 12 by transmitting on the line which is not used for data a clock pulse controlling synchronization of the transmission if the transmission is correct that is.