M03a was a variant of M03 that would occasionally replace it on its schedules. It was an alternative null message format, that included an additional, middle 3-figure segment in the ID (either "111" or "333").
|287||/||111||/||00||BT BT 0 0 0|
|287||/||333||/||00||BT BT 0 0 0|
|Repeated for 5 minutes|
More or less regular transmissions ceased in May 2000. Revived once in a test transmission (121/111/00) in April 2004. Years later, in mid-2010, the voice counterpart E11c surfaced.