The invention concerns a method of pointer processing a digital TDM data stream at a node of a synchronous SDH transmission network so as to justify the data stream on transmission, the data stream having a specified line frequency and being composed of frames, each frame containing a reference word, and the node of the transmission network having a node frequency, the method comprising storing the incoming data stream in a buffer store at the node, using the line reference of the incoming data stream to extract a data pointer from the data stream for each frame, which data pointer indicates the location of the reference word of that frame in the buffer store, and characterised in that a timing pointer is extracted from the incoming data stream utilising the line reference and a line clock the frequency of which is a multiple of the line reference; the timing pointer so extracted is converted into a reference value by utilising the node reference and a node clock; the reference value is utilised to generate a node timing pointer; the node timing pointer is compared with a read address and data pointer; and read-out from the buffer store is justified in accordance with the results of the comparison.