By this we mean that the pedalboard is concave with a 32 note availability. By use of couplers, the stops on this division can be played from any manual indicated, including the pedal. An antiphonal is a optional and separate division of an organ that may be used for special effects or in conjunction with the main organ. It is often placed at the opposite end of the sanctuary for echo effects. If you could perceive each manual plus the pedals as its own separate organ, it is easier to understand the role of the inter-manual coupler.
Couplers usually take the form of tablets located in a row, just above the upper manual.
With this mechanism an entire division can be linked to another keyboard. If the instrument is average to small in size, couplers can increase the flexibility and tonal possibilities. This mechanism allows the entire division to be played against itself an octave higher or lower, or to be silenced altogether, called unison off. Sub-couplers are at a 16' pitch level and sound one octave lower than the fundamental pitch. Super-couplers are at the 4' pitch and sound one octave higher than the fundamental pitch.