|Base price||75 zm|
|Monster use||Will not be used by monsters.|
A stethoscope is a tool used to determine the status of a monster and to listen to dungeon acoustics. It mimics the real life medical instrument used by doctors to examine a patient's heartbeat, hence Healers in NetHack get a stethoscope as part of their starting inventory.
The stethoscope is used by applying it in a direction; this can be to yourself, to a square next to you, or up or down. Its use is free once per action, meaning that it doesn't count as your action for that turn. Applying it twice in a row will cost you the turn. Two stethoscopes don't give you two free uses (but saving and restoring does). A cursed stethoscope has a 1/2 chance (50%) of just sounding your own heartbeat. As of version 3.6, stethoscopes will not function while you are deaf.
When applied to a monster, the stethoscope shows you the name, alignment, experience level, hitpoints, armor class and miscellaneous attributes of the target. Such attributes are generally impairments, but can be any of: tame, peaceful, eating, cancelled, confused, blind, stunned, asleep, can't move, meditating, scared, trapped, fast, slow, concealed, invisible, held by you, digesting you, engulfing you, holding you or carrying you. It will also tell you if the monster is a shapeshifter, which may be a chameleon, doppelganger, sandestin or vampire (but not a werecreature).
When applied to yourself, you are given an accurate appraisal of your alignment, your level, HP, and AC, and any of: dying from food poisoning, dying from illness, solidifying, becoming slimy, being strangled, nauseated, confused, blind, blinded by sticky goop, covered by sticky goop, stunned, injured leg(s), slippery hands, trapped, fast, very fast, concealed, invisible, holding <monster>, or held by <monster>.
When applied to walls you listen to dungeon sounds finding the secret doors and the hollow tunnels hidden behind them. If a secret door or passage is there, you are guaranteed to find it. This does not exercise wisdom.
- "The <monster> interferes"
- You applied the stethoscope while engulfed by a whirly monster (33% chance of interference, 10% for healers ). This effectively examines the engulfing monster instead.
- "You barely hear faint splashing."
- You applied the stethoscope up or down while underwater.
- "You hear the crackling of hellfire."
- You applied the stethoscope to the floor of the castle, beneath which lies Gehennom.
- "The <floor> seems healthy enough."
- You applied the stethoscope down.
- "You hear your heart beat."
- The stethoscope is cursed.
- "You hear a faint typing noise."
- You applied the stethoscope to the edge of the map.
- "The invisible monster must have moved."
- You applied the stethoscope to an I which represents a monster which is no longer there.
- "You hear a hollow sound. This must be a secret door/passage!"
- You applied the stethoscope to a wall concealing a secret door/passage.
- "You hear a voice say, "It's dead, Jim."
- You applied the stethoscope down, to a corpse, while hallucinating.
- You hear a voice say, "You're both stoned, Jim."
- You applied the stethoscope to a statue, while hallucinating.
- "You determine that this/that unfortunate being is dead."
- You applied the stethoscope down to a corpse/towards a square containing a corpse.
- "You determine that this/that unfortunate being is mostly dead."
- You examined a corpse that will revive, as a Healer. 
- "The <monster> appears to be in fine health for a statue."
- You applied the stethoscope at a statue.
- "The <monster> appears to be in extraordinary health for a statue."
- You examined a statue on a statue trap, as a Healer. 
- "The <monster> appears to be in remarkable health for a statue."
- You examined a statue containing items, as a Healer. 
- "You hear nothing special."
- You applied the stethoscope at something else (e.g. a boulder).
- "You can't hear anything!"
- You applied the stethoscope while you are deaf.
Although a stethoscope is not essential for survival it becomes an excellent source of tactical data when used early and often. Therefore, it is one of the most frequently used tools and it's a good idea to #adjust the stethoscope's inventory letter to something memorable like the letter s.
An important use of the stethoscope is to keep your pet healthy. Consistently using the stethoscope allows you to gauge the experience levels your pet is gaining and determine when it has reached its maximum XL. This information becomes invaluable when attempting the protection racket since you are completely dependent on your pet. The stethoscope also enables you to escort your pet to a safe area when its hit points are critically low, using either a whistle or a leash.
Another use is to determine hostile monsters' armor class and to infer the enchantment of the armor on their corpse.
Blind heroes (or those without see invisible) can use it to remove I symbols. Normally, running into one would consume an action.
In wizard mode, it diplays tameness, apport and hunger of pets.
A stethoscope reports unaligned monsters as chaotic. The reason is, that unaligned monsters have an alignment of -128, which is a magic number for unaligned. For other purposes, like your alignment record the code checks specifically for this number, but for the stethoscope it is just a negative number, so it reports it as chaotic. The only unaligned monster (with unaligned alignment in MONST.C) is the Wizard of Yendor. Further some monsters like Angels, Minions or Priests of Moloch have an unaligned alignment in their EPRI or EMIN structure, which overwrites their alignment in MONST.C. These monsters are found in Moloch's Sanctum, on the Astral Plane or if Moloch smites you.
This bug is fixed in NetHack 3.6.0.
In Slash'EM Extended a stethoscope may randomly break upon use. If it's blessed, it will also display extra information including apport, hunger level and tameness of pets, like in wizard mode in Vanilla. The bug that allows players to use it without losing a turn after restoring the game has been fixed.
- src/apply.c in NetHack 3.6.1, line 325
- src/apply.c in NetHack 3.6.1, line 358
- mstatusline in src/priest.c in NetHack 3.6.1
- src/priest.c in NetHack 3.6.1, line 966
- ustatusline in src/priest.c in NetHack 3.6.1
- src/apply.c in NetHack 3.6.1, line 417
- src/detect.c in NetHack 3.6.1, line 1625: Finding these by searching in particular exercises wisdom.
- src/apply.c in NetHack 3.6.1, line 309
- src/apply.c in NetHack 3.6.1, line 263
- src/apply.c in NetHack 3.6.1, line 284
- src/apply.c in NetHack 3.6.1, line 286
- include/align.h in NetHack 3.6.1, line 18