Drop and insert

In a multichannel transmission system, a drop and insert is a process that diverts (drops) a portion of the multiplexed aggregate signal at an intermediate point, and introduces (inserts) a different signal for subsequent transmission in the same position, e.g. , time slot[?] or frequency band, previously occupied by the diverted signal.

Note 1: Signals not of interest at the drop-and-insert point are not diverted.

Note 2: The diverted signal may be demodulated or reinserted into another transmission system in the same or another time slot or frequency band.

Note 3: The time slot or frequency band vacated by the diverted signal need not necessarily be reoccupied by another signal. Likewise, a previously unoccupied time slot or frequency band may be occupied by a signal inserted at the drop-and-insert point.

Source: from Federal Standard 1037C and from MIL-STD-188