Yellow alert
A yellow alert or condition yellow was the second highest alert signal status on Starfleet vessels and starbases, one stage below red alert. It designated a ship-wide state of increased preparedness for possible crisis situations.

Usage 
In this status, a ship's defense fields were energized, and/or the deflector shields were brought to full power, but the weapons systems remained off-line. (; ; ) Depending on the situation, the captain could order a reduction in the closing speed between itself and any potential incoming threats. (; )

A yellow alert could either be activated manually by the commanding officer in preparation for a tactical or environmentally hazardous situation, or automatically upon detection of unknown or hostile spacecraft, or upon detection of certain system malfunctions. If the situation escalated, the commanding officer or the main computer would order a red alert. ()

Notable uses

When the hijacked  went on an intercept course against the , Admiral James T. Kirk ordered a yellow alert. ()

Yellow alert was not typically ordered in the Earth Spacedock. However, in 2285, such an order was given aboard the  when Admiral Kirk was stealing the Enterprise. ()

In 2286, after the  lost power when the Whale Probe transmitted a call on an amplification wave of immense power at the starship, the vessel's captain ordered a yellow alert. ()

In the 24th century, Starfleet Regulations still called for a Federation starship to go to yellow alert when targeted by a laser weapon from another vessel. ()

In early 2365, when the  was approaching a void in space, Lieutenant Worf recommended that the ship go to yellow alert. When pressed by Captain Jean-Luc Picard for this recommendation, Worf responded that he was thinking about an old Klingon legend about a large space beast that devoured entire ships. ()

The following year, Admiral Haden informed Captain Picard that all Federation starships were on yellow alert in preparation for a possible Romulan invasion from Nelvana III. ()

That same year, in the wake of the Borg threat, William T. Riker ordered a standing yellow alert on the Enterprise-D. ()

In 2369, Commander Benjamin Sisko ordered yellow alert when an alien vessel from the Gamma Quadrant arrived via the Bajoran wormhole. ()

The same year, Commander Sisko ordered yellow alert when the imaginations of the people aboard Deep Space 9 became reality. ()

In 2372, Captain Benjamin Sisko told Major Kira Nerys to keep Deep Space 9 on yellow alert as he embarked on a mission to Cardassian territory on the  with several other members of the station's crew. ()

The next year, Captain Sisko put DS9 on yellow alert after learning the Dominion was about to invade the Alpha Quadrant. ()

In 3189, Argeth was placed on yellow alert after Starfleet received intel that the Emerald Chain might make a move on the planet. ()

External link 
 

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Alerts