Recommendation R.105 Replace by the following: DUPLEX MULDEX/CONCENTRATOR, CONNECTING A GROUP OF GENTEX AND TELEX SUBSCRIBERS TO A TELEGRAPH EXCHANGE BY ASSIGNING VIRTUAL CHANNELS TO TIME SLOTS OF A BIT-INTERLEAVED TDM SYSTEM (Malaga-Torremolinos, 1984; amended at Melbourne, 1988) 4.6 The element "C" of the second start-stop character (FIgure 1/R.105) is used for parity check. A parity check element should correspond to the even number of elements in Z condition. Element "C" of the first start-stop character remains vacant and may be used for service purposes. 4.7 FIGURE 1/R.105 Structure for transmission of the conventional number in the virtual channel