Wireless Telephony for Ship's' Trials.
From "The Marconi Review"

An important activity of the sea trials of the White Star Liner "Britannic" was the use of Marconi wireless telephone sets fitted aboard and in the builder's offices. This enable the observers and engineers at sea and ashore to keep in constant communication.

This was the first time that the wireless telephone was used during a ship's sea trials and the innovation proved of such value in exchanging reports about the performance of the new ship that as soon the trip was completed, Messrs. Harland and Wolff, the builders, applied to the Post Office for permission to install similar facilities in the "Innisfallen", a new ship which they had just constructed for the City of Cork Steam Packet Company. Sanction was given and the utility of the Marconi telephone was again so marked that the installation of this equipment became an important factor in ship's trials in the future.

The trials of the "Britannic" and the "Innisfallen" were held in the Clyde Estuary at a distance up to 150 miles from the builder's yards and immediate communication was maintained throughout the trial thus saving time and expense in many areas.

The telephone equipment fitted on these vessels and at Harland & Wolff's offices at Belfast was installed. by the Marconi Company and is known as the Marconi Type YC4. It is a combined transmitter and receiver having a power output of 500 watts.

Receiver tube count: The YA1, YB1 , YC3 , and YC4 transmitter/receivers all used a "Q" valve as a detector and V24 valves in the RF amplifiers.  One valve was a note amplifier which  means an audio stage amplifier stage. Both valves types were first made in 1916 which means that this set was designed after that date

Speaking from Messrs. Harland and Wolff's offices in Belfast to the Britannic in the Clyde River. (From The Marconi Review)

 
Contributors and Credits:

1) The Marconi Review Magazine. Article date unknown. Suspect it is 1914.
2)  Lewis Bodkin  <05bodkin555(at)gmail.com>

Mar 4/19