Also known simply as a "duress code," this is any memorized code word, phrase, or action dropped into a message or conversation to discreetly convey a distress call to someone without unwanted or eavesdropping third parties realizing it.
This is an important device for any undercover operative (detectives and spies, say), who can't just "call for backup" if they get into trouble because it'll blow their cover (if not their head), but really anyone can arrange a code ahead of time — you never know when being Crazy-Prepared will pay off. It's incredibly useful if you have to issue a Quiet Cry for Help.
As a type of Spy Speak, the code should (for obvious reasons) be easy to remember and easy to work into a harmless conversation without sounding suspicious or off-topic. At the same time, it also can't be something that the character might wind up saying coincidentally in ordinary conversations (i.e. a false alarm).
Mind that this only applies to codes that are agreed upon in advance of their usage - see Out-of-Character Alert if the speaker has to improvise a distress code on the spot (because if so, even the intended recipient may fail to notice the signal until later).
Using such a codeword can make a Quiet Cry for Help more subtle and reliable. Compare Trust Password, which is typically used to provide a sense of safety as opposed to warning about danger. Also compare Safe Word for code words often of a more... Freudian nature.
- Wonder Woman Vol 1: Diana and Steve Trevor have developed a series of handy codes and phrases to clue each other in when they've got to give a message saying one thing but the real danger is another. At one point Steve is quite annoyed when Darnell reads a message to Steve from Diana and takes the danger written about within at face value, despite him knowing his agents have such a code, and not only misses the message that Di is captured but also that she was forced to write the letter and the danger is elsewhere. This nearly causes an interplanetary war when the attempted assassination of the Ambassador of Saturn is not prevented until very nearly after the last minute.
- At the beginning of The Negotiator, Danny Roman flashes hand signals (1, 2, and 3 fingers) to alert the sniper team when to fire. The "1" signal is worked into his conversation with the hostage taker as a "wait a minute" gesture, while the "2" and "3" are displayed by him holding his hand to his chest with his back turned to the suspect, but in clear view of the sniper team.
- Running Scared (1986). Police detectives Hughes and Costanza force Snake to go undercover with a hidden microphone to set up the drug lord Julio. They tell Snake that if he gets into trouble he should say "snakebite" and they'll come rescue him. He does, but it turns out to be a trap organised by Snake and Julio.
- A variation in The Bourne Ultimatum. Nicky, a CIA agent, has just unexpectedly entered a CIA office where Bourne killed two hitmen. The CIA calls the office to check what's going on. As part of standard procedures, they give Nicky a one-word sign, to which she needs to respond with a countersign: either the "normal" countersign, or the "duress" code. Even though Bourne is right in front of her and pointing a gun at her, she responds with the "normal" signconfirming that she's sympathetic to Bourne and wants to help. However, she'd already acknowleded that Bourne had been there and agents were down, so her contact tells her that a response team is one hour away, when they're actually five minutes away. Fortunately, she knows he's lying, and guesses she and Bourne have three minutes.
- Hancock: When Hancock is in the middle of his Heroic BSoD, he stops at a liquor store. The clerk rings up $91.10 for one bottle of scotch, which Hancock reacted to angrily at first until he realized how stilted and freaked out the clerk was. The clerk then covers up the zero on the register screen with his finger, signaling "911" and alerting Hancock to the gunman under the counter holding the clerk hostage.
- Triple Cross (1966). The protagonist, a British criminal recruited as a German spy, is told to leave out his callsign XXX if he's been captured. However he has no intention of working for the Germans, so surrenders to police and works as a willing Double Agent for British Intelligence.
- In Half Baked, the protagonists show up to a drug deal wearing wires, with instructions to use the code word "abracadabra" to summon the cops if they find themselves in danger. Unfortunately, the cops monitoring the wire get too stoned to respond, leaving Our Heroes awkwardly trying to play the phrase off as hip new slang.
- Early in Sudden Impact, Detective "Dirty" Harry Callahan goes to a diner he regularly frequents and orders his usual (which includes black coffee). The waitress pours a ludicrous amount of sugar into the coffee while standing in front of him and making pointed glances at certain people in the diner. Harry correctly interprets this as meaning that said individuals are robbers trying to pretend that nothing's out of the ordinary until the policeman who just walked in leaves.
- In The Evening News, a news anchor describes to his wife some of his prearanged visual codes to alert people if he's ever kidnapped and forced to send a video message. This comes in handy later when his wife and son are themselves kidnapped by a South American drug kingpin.
- In The Famous Five a standard covert distress call is for George to sign her name 'Georgina' (something that she hates doing) whenever the bad guys inexplicably ask the captured children to send a note to the non-captured ones, to alert them that something is wrong.
- In The Hobbit, when Bilbo is preparing to sneak up on some trolls, he's told that should he get into serious trouble, "hoot twice like a barn-owl and once like a screech-owl, and we will do what we can" — however, it turns out Bilbo doesn't actually know how to make the correct owl sounds, so it doesn't do him any good.
- In Lucifer's Hammer there are two sentries guarding the settlement at any time: an outer sentry to talk to people trying to enter, and a hidden inner sentry who watches and guards the outer sentry. If the outer sentry raises both hands over his head, this is the signal for the inner sentry to shoot the person at the gate, presumably because that is the one gesture least likely to get you killed if someone is pointing a gun at you.
- Han Solo's Revenge inverts this. Han is being marched back to the Falcon at gunpoint, warned to not make any suspicious moves. This is fine, because Chewbacca is waiting for him to give the all-clear signal, and deploys the ship's guns when he doesn't get it.
- Mentioned on the Death Lands book "Pandora's Redoubt". The Companions use a variety of names when greeted by a scouting member for certain actions, like "all clear", "run away" or "kill the guy with me". They explicitly mention that if they use anybody's real name in such a context, they have been coerced somehow and the Companions must shoot the member, whoever is with them, and run the hell away really fast.
- The girls of The Baby-Sitters Club create such a code to use in case one of them is babysitting and hears a prowler. In a subversion, it turns out that they can't remember the code phrases five minutes after creating them, much less in an actual stressful situation.
- Prince of the City, by Robert Daley (later made a film). Two crooks hear a rumor that the protagonist Robert Leuci is working with the DA to expose corruption, and grab him off the street to interrogate him. On two occasions he's able to get to a phone, call the DA's office and give the distress code. Unfortunately the secretary doesn't recognise the code (it's along the lines of "I can't make breakfast", so doesn't sound urgent). Fortunately a member of the Mafia vouches for Leuci, so he's let go and makes his third call. This time the apologetic secretary puts him through immediately, the DA having returned to his office and realised what's happened. After this cockup, Leuci insists that streetwise NYPD cops be included on his protection detail. This saves his life later when Leuci gives another distress signal (involving scratching his head) only for his backup to assume It's Probably Nothing. A cop among them realises otherwise, yanks out the ignition key to forcibly stop their car, and goes to Leuci's rescue.
- In Rainbow Six the security firm monitoring the silent alarm in the Austrian investor's manor/castle have a short duress signal conversation over the phone with a member of staff. They feign being a vet calling about the horses, so as not to alert anyone who might be listening to the call.
- Tom Clancy used one previously in Red Storm Rising, when a young American officer finds himself trapped behind Soviet lines on Iceland. His handlers tell him that if captured, he is to say that things are "Going great." Cue numerous variations of "Things are lousy," "Things could be better," etc. when Mission Control asks how things are going.
- In a considerably less dire example, Area 7 mentions that Gant and Mother have a set of code words that they say when they want out of a conversation, so the other can intervene. When Gant receives a necklace from an Abhorrent Admirer who just won't leave, she offhandedly begins describing another one she saw in Paris ("Paris" being the relevant code word), upon which Mother loudly and profanely points out the rather impressive military complex they're approaching.
- Brotherhood Of The Rose by David Morrell. The CIA are following Rogue Agent Saul until he makes contact with his surrogate brother Chris and they can both be killed. When Saul sets up the meeting, an underling urges spymaster Elliot to let them grab Saul and sweat the meeting place out of him. Elliot turns this idea down, pointing out that Chris and Saul have known each other since they were children and have codes and passwords dating back to then, so they've no way of being sure that Saul couldn't pass on a hidden warning.
- In Robert A. Heinlein's novella "If This Goes On" the protagonist is being arrested. He argues that he has the right to appear in proper uniform, and in the process manages to arrange a sweater on his bed in the form of a distress signal. His roommate picks up the message when he returns and sets up a rescue.
- Known Space. Played with in The Long Arm of Gil Hamilton. Gil is investigating a case of Organ Theft, so arranges for a police psychic to check his safety at regular intervals. Except the only 'slot' she has free for him is 9.45am. He's later abducted on his way home at night, then wakes up in an anonymous apartment with no way of knowing what time it is. He only survives because the psychic got worried when Gil didn't turn up for work and checked him early.
- Modesty Blaise novels:
- In A Taste for Death, Modesty and Willie are having a radio conversation when Willie mentions that Jacqueline has come to visit, a pre-arranged code meaning that he's in danger.
- In The Impossible Virgin, the villain's security measures include a hand-signal (pretending to adjust their tie) that his men have to do when they return to base to signal that they're not under duress and it's safe to open up and let them in.
- Use of Weapons. A Properly Paranoid dictator has his own bedchamber under surveillance, with a verbal codeword to alert his guards. Unfortunately the assassin who turns up in the middle of the night has access to superior alien technology, so he's already taken care of the cameras, deactivated the microphones and unloaded the hidden pistol.
- The cold open of one of the Honor Harrington novels has a scene where a transport is transmitting a code which doesn't mean 'I'm being boarded by pirates', but 'I have been boarded and taken by pirates' and the communications officer notes that he's never seen it used outside of simulations. It turns out the owner of the transport was a bit paranoid and set it up to be used only if its identification was requested by a warship after a pirate attack.
- In the webnovel Les Aventures de Morgoth, the ciminal mastermind known as the Black Queen has set a special trigger with the demon who maintains her Teleport Interdiction, to lift it if she praises her worst enemy three times in a row. It works even if she doesn't know whom she's praising, which is exploited by a prisoner of hers.
- In Andromeda, Dylan Hunt blinks "AC 145" in Morse code during a message he sends to the ship that supposedly states that all is well. "AC 145" means no, he's been captured.
- On The A-Team "Red Ball One" and "Bag is Leaking" mean "big trouble" and "one of the team took some lead" as explained to Amy by Murdock, who receives the code from the team.
- On Flashpoint the leader of the SRU team is taken hostage but the rest of the cops are unaware of this. He is told to give his team instructions over the radio as normal and direct them away from the hostage taker. He complies but tells his team members to "stay frosty" — his team's code word for a situation like this.
- In a fifth season episode, a nurse is kidnapped and forced to make a call to her significant other that she is working late. However, she is not the first nurse to be kidnapped, and so drops the pre-arranged distress code (Dr. Armstrong) into the phone call.
- The main characters of Blue Bloods, all related to each other, have been trained if they are held captive and one of their family members says to the capturer "please don't hurt my family" they are to drop to the ground immediately, allowing the speaker to attack directly.
- In An Idiot Abroad, Karl's distress code in case he gets kidnapped in the Middle East is "congress tart".
- Rookie agent Nikki Bentencourt is sent undercover to catch a group of people kidnapping ATM users and is given the distress code "Mexico" to use if the operation starts to go south. It does, but she's too stubborn to use the word, believing that she can salvage the operation on her own. Don is not happy.
- Later on, when Colby is in a hostage situation, David says that he could ask the FBI to "send out for Mexican" to discreetly let them know that a tactical entry was imminent.
- This had been done once before, this time with David as the hostage. SWAT is getting ready to breech, but want to give David a heads-up so he'll have an advantage over the bad guy, so Don, who had been trying to negotiate, asks the suspect if he thinks he can "just get on a plane to Mexico". Unfortunately, despite David understanding the hint, the shooter still gets the upper hand; in the end, David has to take control and talk the guy out himself.
- When Neal Caffrey of White Collar has to go undercover as a foreign man named Mr. Black (whom he assumed was a courier at the time), he is told that if anything bad happens, he should use the words "long flight" to alert Peter. Subverted in that when he discovers that Mr. Black is a hitman and not a courier, he attempts to use the phrase and fails because the criminals have employed a signal jammer.
- Star Trek: The Original Series:
- "Bread and Circuses". "Condition Green" means that the landing party has been captured, they are being forced under duress to communicate with the ship, and that the ranking officer aboard ship is to take no action at the present time. It does not prevent the ranking officer from preparing to take action later, or to exploit any opportunity to rescue the landing party.
- Star Trek: The Original Series episode "Day of the Dove". When Captain Kirk and his landing party are captured by Klingons, he pushes an emergency button on his communicator, warning the Enterprise. When Scotty beams them up he materializes only the Enterprise crew, leaving the Klingons suspended in transit. When the Klingons are finally materialized they are easily captured.
- This communicator emergency signal is actually revealed to exist two seasons earlier...unfortunately, in that case, it's activated accidentally by a 1960s MP. The result is...not ideal.
- In Burn Notice:
- Ex-spy Michael and ex-terrorist Fiona have developed a number of ordinary phrases they can drop into a conversation to convey meanings like, "this is a trap, be alert" or "this phone call is being made under duress, don't believe anything I'm saying" or "get on the floor and cover up." The last was one Fiona's father taught her and her siblings.
- One time, when the FBI were waiting at Michael's mother's house to arrest him, on the phone call to Michael, she uses the exact same phrase she would use when her abusive husband was on a tirade and she wanted Michael and his brother to stay away from the house.
- In a ninth season CSI episode, Riley communicates to Greg that the situation is normal, but calls him by her name to indicate that she is speaking under duress. Greg responds by calling Riley by his last name to indicate he understands. This was something the team was demonstrated practicing during a drill earlier in the episode.
- In CSI: Miami, it is eventually discovered that a woman died because her handler ignored her coded call for help.
- Employed several times in 24, the most famous instance being early in Day 5, when Jack Bauer is being forced to misdirect CTU's assault teams into an ambush by the terrorists. He slips the duress code "flank two" into his radio conversations, but CTU initially fails to pick up on it, since their duress codes have been changed in the two years since they fired Bauer.
- During a con in Leverage, Nate and Sixth Ranger Tara are held at gunpoint by a Corrupt Corporate Executive and Triads who demand $50,000. Tara tells Nate to get the fifty thousand: "Fifty thousand, ok, five-o, do you understand, five-o?" The "five-o" is an explicit covert alert for Nate to switch the con they had been running to one that involves bringing in the police.
- In Terra Nova, Cowboy Cop Jim Shannon teaches his family this trick, which comes in handy when his daughter Maddy is kidnapped by a murderer.
- In "Bête Noire", Ducky and his assistant Gerald are held hostage in Autopsy. Ari, the hostage taker, needs evidence that is now in Abby's lab. So, while on speaker phone, Ducky yells at Abby he needs the evidence back "stat." "Stat," as Gibbs and others later note, is code for a medical emergency requiring immediate help. As the "patients" in autopsy are typically dead, Gibbs realizes there is a lot more going down.
- Played with in the episode "Judgment Day." Director Shepard dismisses Tony and Ziva (her security escorts) before going on a dangerous mission. When they call to check up on her, she doesn't use the duress word, so Tony thinks she's OK while Ziva is still concerned. They later find her in an abandoned diner, having been shot and killed.
- A troubled young man takes hostages and demand to see his mother. The off-site agents find out that said mother is listed as "deceased". In order to get this information to the on-site agents, they give the name of one of the now-deceased Agent Catlin Todd as the one who is handling the case.
SWAT Officer:How are you going to tell Gibbs that the kid's mom is dead?
Dinozzo: I already did. Special Agent Todd is dead
- Buffy the Vampire Slayer. In "First Date", Xander text messages Willow a codeword that means either "My date is a demon who's trying to kill me - send help!" or "Don't call me because I'm about to score!" Unfortunately as it's been several years since Xander went on a date, Willow has forgotten which one it is. They play the percentages and rescue him. As the demon was an attractive woman who asked Xander on a date, we never discover which code he sent.
- Angel. Angel Investigations doesn't have one, so when Lorne is held captive in Las Vegas, he keeps asking about 'Fluffy' (a non-existent dog) when calling his friends. Unfortunately one of Lorne's character tropes is The Nicknamer, so no-one is suspicious.
Winifred: You don't think he was referring to anything of mine that's fluffy, do you? Because that would just be inappropriate.
- Lampshaded by Lorne himself in "The House Always Wins", yelling at them about it when they finally realize he's in trouble.
Lorne: "Fluffy. Fluffy the dog. The dog you don't have. The universally recognized code for "I'm being held prisoner. Send help!""
- Lampshaded by Lorne himself in "The House Always Wins", yelling at them about it when they finally realize he's in trouble.
- Doctor Who
- In "Warriors Gate", experienced companion Romana does a tongue-in-cheek version where she tells new companion Adric that the signal is her putting her hands up. She is later invited by the villains back to their spaceship; aware it's a trap, she does an elaborate stretching gesture that just happens to involve putting her hands over her head.
- In "Day of the Daleks", the Doctor uses contemporary slang that the soldiers holding him prisoner don't understand, as they've time-travelled from the future.
Doctor: I assure you, Brigadier, there's nothing to worry about. Tell Styles that. Tell the Prime Minister. And, Brigadier, be particularly sure to tell it to the Marines.
- Wiseguy. Undercover cop Vinnie Terranova calls his Uncle Mike (actually 'Lifeguard', his Mission Control) and says he can't make breakfast. At one point he's arrested by the local police and has to shout to the woman with him as he's dragged off to relay the message. She does, but knows there's something suspicious as she's Vinnie's cousin, and he doesn't have an uncle called Mike.
- Sherlock has one between Sherlock and John: "Vatican cameos." The second time it's used, John explains that it means "battle stations, someone's going to die."
- Supernatural. In "Hunted", Gordon has captured Dean and gets him to call Sam to their location. Dean tips him off via this method (the codeword is "Funkytown"), but Gordon is savvy enough to anticipate this and rig the back door with a Booby Trap for when Sam tries to sneak up on him.
- Enemy at the Door is set in German-occupied territory during World War II. In "Call of the Dead", a character who's been sent to a German-run prison writes home to his family assuring them that things are going well for him, and marks off the bit that's actually true from the rest that's lies because he wouldn't be allowed to tell the truth with a mention of a non-existant friend named Betty Martin, a reference to the expression "all my eye and Betty Martin".
- In the Elementary episode "Rat Race," Sherlock had been texting Joan in illegible acronyms. When he's kidnapped by the Murderer of the Week, he texts her back, saying he's fine, but in straightforward, grammatically correct English. This tips Joan off that something's not right.
- The Bill. The detectives arrest an Eastern European drug dealer and force him to set up a drug buy. They insist he speak English while making the call to avert this trope, but when no-one shows up the dealer smugly points out that they never speak English while making a deal in case they're overheard, so this trope happened anyway.
- In an episode of Get Smart, the Chief is undercover as a singing waiter, and alerts Max and 99 to a KAOS agent by using the CONTROL Singing Code, substituting words like 'cigarette' in the lyrics while singing Alouette.
- In The Orville, the phrase "13 button salute" means that the ship has been compromised and advises the recipient notify Union Central. Unfortunately, the Kaylon know about the phrase from Isaac, and when Captain Mercer uses this code to warn the USS Roosevelt of the situation, the Kaylon destroy the Roosevelt.
- In The Mysteries of Laura, when Laura is held at gunpoint in her room by the suspect of the week, she gets the babysitter to leave by saying she has food poisoning from bad clams. The sitter relays this to the police captain, Laura's ex-husband, who knows Laura doesn't eat clams and figures this means she's in trouble.
- In Alias, Jack is identified as a CIA mole by the new head of SD6 and imprisoned. He's ordered to get Sydney to SD6 HQ so she can be captured too. When calling her, he adds "Oh, and take surface streets, they're doing some work on the freeway."; she recognises this as their private duress code, allowing her to mount a rescue.
- In the Agents of S.H.I.E.L.D. episode "Collision Course Part 1", Simmons, who is on a spaceship heading to Earth with the Big Bad, finally gets the comms system working and gives a SHIELD code (supposedly her own ID) to Davies. To her surprise, Davies, held hostage on the Zephyr by a Well-Intentioned Extremist preparing to blow up the spaceship, gives it right back.
- Firefly: Simon explains that, after his genius sister River was inducted into an Extranormal Institute, writing letters became her only form of communication with the family. After a while, the letters changed: they were full of references to events that never happened and people they never knew. Simon cracked the code, which said "they're hurting us, get me out."
- When Saffron's "husband" Durran discovers her and Mal's plot to steal his Lassiter, she taunts him, saying that if he had any brains he would have called the police the moment she came back unannounced. He replies "Oh, I did.", and shows her his ring, which contains a transmitter that sends a distress signal when pressed. And indeed, on rewatching the scene where he first comes back, you can see him casually press the ring on his finger when he sees Saffron.
- Las Vegas: The operations crew, who monitor cameras of all the happenings in the Montecito Casino, are trained to have use certain phrases in case of emergencies. If the ops center itself has been compromised by hostage takers, then they are to use the phrase "Nothing but aces" to alert others of the danger.
- Modesty Blaise: If Modesty or Willy insert the name 'Jacqueline' into a conversation, the other knows that they are under duress and not able to speak freely.
- The List of Character Survival Techniques Version 1.5, as a guide to RPG players, includes the following tip:
The party should have a short list of subtle signs, with meanings like:"Something is wrong, try to leave unobtrusively.""Get ready for a fight.""Get ready to run like hell."
- The trick-taking card game Kemps uses a form of distress codes as its key mechanic. Each player has a partner, and the teams take turns drawing and discarding from the deck, trying to be the first to get four of a kind. Once one member of a team has the right combination of cards, they must secretly signal to their partner in some way; if the partner shouts "Kemps!", the team takes that trick. The link can be a seemingly innocuous gesture (such as running hands through hair or adjusting glasses), but is just as likely to be a certain phrase. Players who use that strategy often chatter throughout the hand, so that the other teams (who can say "Block Kemps" if they think their rivals are signaling each other) don't know what part of the conversation is important.
- The Halo novels established the Spartan-IIs' classified distress call as a simple "Olly Olly Oxen Free". It makes a rather ironic reappearance in Halo 5: Guardians.
- Mass Effect:
- Quarians returning to the Migrant Fleet have a code phrase that indicates they're in danger. It's a sign of how loyal Quarians are that they know full well that giving the duress code signals security to fire on their ship. They also have a second phrase that indicates their mission was successful and the ship they're aboard is no danger to the Fleet; Tali'Zorah's is "After time adrift among open stars, along tides of light and shoals of dust, I will return to where I began."
- A side mission in Mass Effect 2 has Shepard approached by a guy who turns out to be the cameraman for a reporter who's trying to do an expose on some gangsters. He's learned that the reporter's cover has been blown so he needs to get her out of there by telling her the code. Unfortunately, he's a Non-Action Guy and therefor is far too scared to approach the gangsters himself, so he gets Shepard to do it for him. The code is simply the words "terminal" and "eternity" worked into a conversation. It works, and the reporter escapes by claiming she needs to use the bathroom.
- A major plot point in New Captain Scarlet episode "Trap For A Rhino". The Mysterons are actually counting on a kidnapped Spectrum agent using her duress code so they can ambush the rescue team and hijack the titular Rhino armoured vehicle, which they intend to use to blow up a nearby nuclear power station.
- One episode of Static Shock sees Ebon and the rest of the Meta-Breed kidnap Richie and hold him in an abandoned apartment complex. To communicate for help, Richie secretly turns on his two-way radio and begins badmouthing Ebon, talking about what a big shot he must feel like for hiding at that particular address. The villain catches on and destroys the radio, but not before Static's heard the message and begins traveling there.
- According to some newspaper stories, Queen Elizabeth II of the U.K. apparently has several signals involving the way she holds her handbag which she uses to signal her staff when, for example, she wants to get out of a conversation with someone.
- Also during World War II, the British government had spies working in occupied Europe, and gave them codes to indicate if they had been captured by the Germans and forced to send bogus data back. Unfortunately, several captured operators would use the code, then their British handlers would say "that's your duress code, don't use it unless you've been captured", and the spies got shot, tortured or turned by the Germans. Strangely, the German intelligence services never seemed to have thought of doing the same with their own agents, all of whom were captured within hours of being landed in Britain and being offered a choice between turning and death.
- Notably, the hapless (and other) British operatives actually used an inverted form of this - they were given certain codes to include in their messages as long as they were free, but deliberately leave out of their messages if they'd been captured. This makes their handlers' mistake slightly more forgivable - one lapse could technically have been an oversight on the agent's part - but still, SOE headquarters seemed to routinely assume their agents were forgetful, rather than compromised, as hastily trained agents often had errors in their coding.
- In a similar vein, an Australian agent sent to East Timor hadn't been issued a distress code, so one was transmitted to him. Problem was, he'd already been captured by the Japanese. Another agent carelessly wrote down his code in his logbook, but was able to convince his captors the word was innocuous... until his handlers in Australia transmitted the word three times in the same message to 'remind' him that he'd left it out. Ironically the ruse was only discovered by someone Reassigned To Australia in punishment for the above-mentioned stuff-up in occupied Europe, who belatedly realised the Japanese were pulling the same trick.
- When Norway was under Nazi occupation during World War II, resistance workers wore paper clips on their shirt pockets to identify each other. It didn't take long, however, for the occupiers to eventually notice.
- Flying a national flag upside down is sometimes said to be one of these, but in fact it's considered an Overt Distress Code; it's a recognised form of Distress Call for ships at sea with non-functional radios. For flags where it's not immediately obvious they're being flown upside down you're supposed to tie a knot in them.
- Before the Iraq War, a soldier let his family know he was about to go into combat by inserting a phrase about the size of the flies into a message to them- which they had pre-determined before he deployed.
- Commonplace in retail security, often with a variety of code-phrases ranging from "observe potential shoplifter in [area]" to "send in-house security" to "call law enforcement" to "missing child in the store."
- Aircraft transponder code 7500 is reserved for use in case of hijacking, 7600 for radio failure, and 7700 for a more general MAYDAY signal. Aircraft using these codes will immediately be highlighted on radar screens, typically by adding a red "EM" tag next to their callsign. note
- Hospitals often have a specific phrase that they use when they need security, but don't want a panic, or for a violent person to know that security is on the way - such as "Paging Doctor Silver to (nearby room)".
- Parents will often set up one of these with their children, so they know when the child needs rescuing from an uncomfortable situation but doesn't want to embarrass themselves in front of friends/peers.
- In American circuses and musical theatre, the playing of Sousa's "The Stars and Stripes Forever" is a covert code to performers and venue staff for "something is very badly wrong, prepare to evacuate the venue".
- British railways, the London Underground and a few other places use the "Inspector Sands announcement", whose meaning is now something of an open secret.
- Police radios have a panic button that sends a distinctive set of tones out over their assigned frequency, but not through the handset's own speakers, to summon assistance without letting a hostage-taker or other armed and dangerous individual know they've been called.
- This domestic violence PSA is based on a real-life incident. A 911 dispatcher picks up a call and is surprised when a woman starts ordering a pizza. He tries to tell her that the line is for emergencies only, but when she keeps talking, he realizes that she's actually trying to get help ("Ma'am, are you in danger?" "Yes, that's right..."). The dispatcher is able to send help and save the woman's life.
- In 2016 in the UK, posters started popping up in venues for people who feel unsafe or threatened while on a date — instructing them to go the bar and to "ask for Angela", notifying staff and discreetly getting them out of the situation.