The method relates to the protected transmission of data (D0-D4), the coding (‘S,’ ‘0’-‘F’) of which is represented, respectively, by a sequence (FR0-FR4) of a predefined number of on and off values (Z1, Z0). A count value (C) representing the predefined number is formed by changing the count direction (F, R) after each on value and incrementing or decrementing the count value with each off value. An error information (F1, F2) is generated if a first end value (EC), which is transmitted together with the data as a coded sequence (SIG) of the count value C, differs from a second end value (EC1, EC2), which, like the count value, is formed from the transmitted sequence. The method is advantageously used in identification systems (IS), in mobile data carriers (DT) and in read-write devices (SLG). This affords the advantage that a data transmission error can be detected quickly and with high reliability by using a simple forward and backward counter (CNT). The counter can be implemented with little circuit complexity by a simple software program or by an electronic circuit, e.g., by a binary cycle counter.