The TS-921 is a Chairman unit of the Infrared Conference system. Since the system is cordless, it can be easily installed and removed. The Chairman unit features a priority speech key which allows it to take precedence over the TS-922 Delegate units when speaking. It can be operated on either the AD-0910 AC adapter or the BP-900A lithium-ion battery. It is equipped with a remaining battery indicator. Two types of dedicated microphones are made available for the TS-921 as optional products: the TS-923, TS-903 standard type and the TS-924, TS-904 long type.