m branches in order of increasing precedence in order of decreasing transmission loss for example within the transitional cable branches inclusive of communicating branches where m is equal to or less than n where n equals the maximum cable branch number 124 u2212 the maximum radio branch number 125 in the radio section addition of the radio branches and switching of them are carried out in response to the finally selected cable branches it is also possible to take such a control method that omits the addition of those candidates which are most likely to be deleted because of their lower precedence than the communicating branches even though they are added as the cable branches the radio branch connection and release image of the addition deletion dho in fig2 indicates that a new branch 92 is added in the presence of branches 90 and 91 at a time 100 the branch 91 is deleted by switching at a time 102 and then a branch 93 is added by switching after the time 102 the point of intersection of the time 102 and the branch 93 is represented by an open circle because the maximum radio branch number is set at three on the other hand the cable branch connection and release image indicates that cable branches 96 and 98 are added and a.