Transmission control method and device, and transmission apparatus

A transmission control device for controlling the insertion of first unit signals into a stream of second unit signals transmitted from a first transmission path having a first bandwidth to a second transmission path having a second bandwidth by assigning points at which the first unit signals may be inserted, comprising the steps of:

• a first arithmetic unit adding a value representing the second bandwidth to a selected value, thereby obtaining a sum value;
• a comparator connected to the arithmetic unit, comparing the sum value with a threshold value representing the first bandwidth, thereby generating an assignment signal designating the points at which the first unit signals may be inserted;
• a second arithmetic unit connected to the comparator, subtracting the threshold value from the sum value, thereby obtaining a difference value;
• and
• a selector connected to the second arithmetic unit, selecting one of the sum value and the difference value as the selected value, responsive to the assignment signal;
• wherein the first arithmetic unit, the comparator, the second arithmetic unit, and the selector operate at unit intervals equivalent to a length of said first unit signals and said second unit signals.