Earphone
The earphone was a personal speaker  connected to the bridge science station of the . Consisting of a flexible cable with a receiver, this device was placed next to the scope on the console. A person would use this device by holding it against their ear. It was later replaced by an earpiece. 

In 2265, with the receiver to his right ear, Spock reported what he was  from the disaster recorder of the  to the bridge crew and department heads. ()

Memory Alpha articles named from scripts
Communications technology