Captain Archer's desktop monitor and two loudspeakers
The speaker was a type of communications device used for converting electric signals into audible sound. Federation and Klingon starship bridges were equipped with speakers.
In 2153, aboard the Enterprise, Commander T'Pol reported to Captain Jonathan Archer that the ship had picked up a conversation between a transport declaring an emergency and a government official on Xantoras. Archer requested the conversation be put on the speakers. (ENT: "The Breach")
Captain Archer placed two small loudspeakers on his desk in his ready room aboard Enterprise. (ENT: "Regeneration")
In 2266, aboard the USS Enterprise, Lieutenant Commander Leonard McCoy contacted the bridge from the dispensary. He had discovered the cause of Crewman Darnell's death, which he didn't want to communicate by the speaker, so he requested that Captain James T. Kirk come see him. (TOS: "The Man Trap")
Later that year, as the Enterprise approached Outpost 4, the starship regained contact with the outpost. Lieutenant Nyota Uhura switched to speakers. Commander Hansen, the outpost's commanding officer, and Kirk communicated with each other via the speakers. (TOS: "Balance of Terror")
Much later that year, the Tantalus Colony sent a message to the Enterprise. Uhura switched the message to the speakers. Kirk acknowledged the message from the colony via the speakers. (TOS: "Dagger of the Mind")
In 2267, aboard the Enterprise, the ship began receiving calls from people on the surface of Omicron Ceti III who had been recently liberated from the influence of the spores. One of the callers was Elias Sandoval. Kirk requested that Spock put him on the speaker, so that he could speak with the colony leader. (TOS: "This Side of Paradise")
In 2269, aboard the Enterprise, Uhura reported to Captain James T. Kirk that the communications equipment was picking up a subspace radio signal from the Taurean system. Kirk requested that the signal be put on the speakers. (TAS: "The Lorelei Signal")
Later that year, aboard the Enterprise, Uhura reported to Kirk that the communications equipment was detecting interference on subspace extreme upper registers from a planet orbiting the star Cepheus. Kirk requested that the interference noise be put on the speakers. (TAS: "The Terratin Incident")
In 2285, during the Kobayashi Maru scenario, Commander Uhura reported to Saavik that the ship was picking up a message on the distress channel. Saavik requested that the message be put on the speakers. (Star Trek II: The Wrath of Khan)
In 2286, aboard the HMS Bounty, Rear Admiral Kirk requested that the message being transmitted to Earth by the Whale Probe be placed on speakers by Uhura. Later, after successfully traveling back in time to 1986 Earth, Kirk again asked Uhura to put a transmission on speakers. This transmission was of a whale song that was being sung by George and Gracie at their home in the Cetacean Institute. (Star Trek IV: The Voyage Home)
In 2293, the USS Enterprise-B picked up a distress call from the SS Lakul. John Harriman requested that his communications officer put the call on speakers. (Star Trek Generations)
In 2366, the USS Enterprise-D attempted contact with the Calamarain. Lieutenant Worf informed Captain Jean-Luc Picard that a signal had been detected, then the tactical officer switched the signal to speakers. (TNG: "Deja Q")
In 2371, aboard the USS Voyager, Lieutenant Commander Tuvok picked up an audio transmission from within a singularity. Captain Kathryn Janeway requested that he put the transmission on speakers. (VOY: "Parallax")
Later that year, the D12-class Bird-of-Prey commanded by Lursa and B'Etor was hailed by the Enterprise-D. B'Etor requested that the ship's helmsman put the message from Captain Picard on the speakers. (Star Trek Generations)