Linn Knekt Basik 3 RCU.
Room Control Unit for subzone control, non-IR-receiving.

Linn Basik3 / Basik3IR RCU

A Main room may feed at least 4 Secondary rooms, each with a Subzone that may listen to the same source its Secondary room with independent volume control.

Linn Knekt Basik 3 IR RCU.
Infra-Red receiving RCU.

Linn RCU, IR-receiving main, secondary, or subzone
Room control Unit (RCU). Linn Knekt RCU brochure
New Linn Knekt RCU Marine Upgrade Kit

What is multi-room audio?  Multi-room audio hi-fi essentials
Linn multi-room audio hi-fi Linn Knekt multi-room Amplifiers
IR control  Niles multi-room amps  C-Bus multi-room audio