Abstract: Methods and apparatus are disclosed for controlling peripheral units in a telecommunication system by means of two or more like control apparatus, wherein the peripheral units are assembled in groups, each of which is associated with its own switching means for selectively connecting the particular group to a control apparatus. The control of all peripheral units to be controlled at a given time is effected with only one of said like control apparatus at that time. Each active control apparatus is caused to time itself for a first predetermined time as to the duration of its control of said peripheral units, and to initiate a timing cycle in another one of said control apparatus for a second predetermined time longer than said first predetermined time. The control apparatus are periodically exchanged in their control function in response to the mentioned self-timing.