Emergency Medical Hologram
The Emergency Medical Hologram (EMH) is a sophisticated hologram developed in the early 2370s by Starfleet and used on most Federation starships in the late 24th century. The first starship to be equipped with an EMH was the USS Voyager. The formal name of the program is EMH Program AK-1 Diagnostic and Surgical Subroutine Omega-323.
Note: An EMH, although a computer-created hologram, cannot automatically access a ship's computer. That would require far more processing capacity than its holomatrix can support. Instead, it accesses the ship's computer like any normal crewmember.
An EMH cannot feel pain, cry, or bleed. If grabbed, it can become insubstantial and slip from its captor's grasp. It does maintain the capacity to learn and adapt to new circumstances. It can provide routine and complex medical care, up to and including detailed surgery, in the event that a ship's doctor is incapacitated.
An EMH system requires sophisticated holoemitters and sensors in the appropriate areas; Starfleet can install one only on ships with the most sophisticated medical facilities. In more modern vessels, holoemitters can be installed throughout the ship, enabling the EMH to go to the sick and injured, rather than requiring them to come to Sickbay.
However, an EMH is for emergencies, as the name indicates, not for everyday use. Starfleet is an organization of sentient, living beings, not robots and holograms. Technology is just a tool, and Starfleet expects its personnel to do their jobs and do them well, even if the EMH outclasses them on medical knowledge. Only when the ship's medical personnel are incapacitated or in dire need of assistance should the EMH be activated. If a medical officer remains alive and able to do their job, they can, in their best medical judgment, overrule any attempt to use the EMH (even by the ship's commander) and shut it off, per Starfleet regulations - and most doctors won't hesitate to do so.
As of 2376, there have been four versions of the EMH, called Mark I, II, III and IV.
First activated on stardate 48315, it was developed by Dr. Lewis Zimmerman at the Jupiter Station Holoprogramming Center as the embodiment of modern medicine. The EMH was programmed with 5 million possible treatments from the collective information of 2000 medical references and the experience of 47 individual medical officers. The EMH was also supplemented with contingency programs and adaptive programs to learn while serving as a supplement of a normal medical staff in cases of emergency. The EMH program was only meant to function for a maximum of 1500 hours (62.5 days); after this time, memory degradation would occur.
The Mark I's outward appearance was a copy of its inventor, Dr. Zimmerman. However, as the Mark II was released, the first version soon became obsolete and, thus, was reconfigured for menial tasks such as to scrape plasma conduits or to mine dilithium ore.
First activated in 2374, the Mark II was designed as an upgrade and replacement for the Mark I. The Mark II was designed to be more pleasant and courteous and its outward appearance was changed. The first starship to be equipped with an EMH Mk II was the USS Prometheus, which enabled full mobility for the EMH, as the whole ship was outfitted with holographic projectors.
The EMH Mk III is in use aboard Starfleet vessels whose mission profiles have them at a distance from Federation planets and bases for an extended period. The USS Atlantis was the first vessel to field-test a Mk III.
Obvious changes are the physical appearance of the hologram itself, now resembling a human woman, and the increased social abilities. Where most humanoids did not like being treated by the standard Mk Is because of its flaws, those who have been treated by Mk IIIs have yet to express any reluctance about a return visit. Mk IIIs have the extended operating durability, as well, being able to run for 7500 aggregate hours before substantial maintenance is required.
The Mark IV was in use by 2377.