Abstract: A PCM codec for converting between PCM words and analog signals has at least one element which is used for both types of conversions even though the clock pulse frequencies of the incoming and outgoing PCM words are different; a timing unit for generating time intervals wherein a first and second number are needed at the very most to carry out the respective conversion operations, the shorter of the period lengths determined by the two clock pulse frequencies includes at least the sum of the two numbers of time intervals; and a control unit for receiving the clock pulses in order to indicate the respective conversion type and for generating conversion type signals by means of which each of the time intervals is associated with one of the two conversion types. In order to control states where a type signal is generated delayed with respect to a notification pulse, the codec includes information memories to store the influenced information.