142 the flow chart reverts to the block 140 when the answer from the block 140 is no n the flow chart proceeds to block 144 in which a check is made to see if there are any size 2 holes if the answer is yes y then in block 146 the size 2 hole is added to the size 2 table the flow chart reverts to the block 144 when the answer from the block 144 is no n the flow chart is terminated at block 148 in operation when a new call is to be made call set up procedures will use the size 1 2 4 and 8 tables to find a suitable hole in which to place the call starting with the smallest size possible and trying successively larger tables until an entry is found the table entries must be readjusted as necessary to reflect the arrival of the new call call clear down procedures upon completion of a call will add the cleared frame s or hole to the appropriate table and call up the tidy up procedure fig7 illustrates an embodiment of a data terminal dt the terminal comprises a low rate data terminal 30 which is electrically connected to a cordless secondary station.