====== Lange L901 ======
{{wst>image_r|Lange_L901.0|Calibre Lange L901.0}}
**Cal. L901.0** is a [[hand-winding]] watch movement from [[A. Lange & Söhne]] and used in the [[Lange 1]].

===== History =====
When [[A. Lange & Söhne]] was preparing to relaunch, they decided to make a splash with a truly unique watch, the [[Lange 1]]. The hallmarks of that watch, and this movement, are the asymmetric dial arrangement and two-window [[big date]]. This latter complication was designed to resemble the 1841 Five-Minute Clock at the Semper Opera House in Dresden and gave the new [[manufacture]] its first patent. Although the dial is not centered, it does have a pattern: The hour and minutes dial, date window divider, and subsidiary seconds dial form the point and two leg apexes of an isosceles triangle, with the power reserve indicator centered at this base.

===== Technical details =====
All L901 calibres are based on this original design, and all feature the same basic complications: [[Big date]] at 1 00, [[power reserve indicator]] at 3 00, [[small seconds]] at 5 00, and hour and minute hands at 9 00. The movement is constructed with a [[three-quarter plate]], made of untreated [[German silver]] and decorated with [[Glashütte Stripes]], in traditional Glashütte style. It features nine gold [[chaton]]s and [[blued]] screws. In all, there are 53 [[jewels]] synthetic [[ruby|rubies]].

For an accurate [[rate]] result the [[screwed balance]] with [[Nivarox hairspring|Nivarox 1 hairspring]] is responsible. It is shock-proofed, makes 21,600 vibrations per hour and is adjusted in five positions. On the hand-engraved [[balance cock]], the [[Swan's neck fine regulation]] is mounted. Its patented beat adjustment mechanism makes it possible to accurately set the impulse pin relative to the pallet fork without removing the [[balance wheel]].

===== Variants =====
  * Introduced in [[1998]], **Cal. 901.1** was a special version of Cal. 901.0 with gold lever and escape wheel and a gold cocks for the balance, lever, and escape wheel. It was used in the limited-edition gold-dial [[A. Lange & Söhne Lange 1A|Lange 1A]], produced from [[1998]] until [[2001]]. Another minor variation is **Cal. 901.4**, introduced in [[2001]], with longer [[pinion]]s for watches with thicker dials, such as [[mother of pearl]].
  * **Cal. 901.5** adds a [[moon phase]] display to the small seconds subdial. It was introduced in [[2002]] for the [[A. Lange & Söhne Lange 1 Moonphase|Lange 1 Moonphase]] and remains in production.
  * The initial [[2003]] [[A. Lange & Söhne Grand Lange 1|Grand Lange 1]] featured the **Cal. L901.2** movement, but the [[2012]] model features a new thinner movement, [[Lange L095|Cal. L095.1]].
  * Calibres **L901.7** and **L901.8** were introduced in [[2003]] for the limited-edition [[Lange 1|Lange 1 "Luna Mundi"]] and were produced only through [[2004]]. These two movements are identical apart from their calibration Cal. 901.7 is calibrated for the Northern hemisphere, while Cal. 901.8 is calibrated for the Southern. They were used in the Lange 1 Moonphase "Ursa Major" and "Southern Cross", respectively, and sold as a set in a limited edition of 101.
  * A smaller variant with moon phase, **Cal. L901.9**, was used in the [[Lange 1 Moonphase|"Little" Lange 1 Moonphase]] in [[2009]] and [[2010]].

The [[tourbillon]] [[Lange L961|Cal. L961]] is based on Cal. L901.

When the Lange 1 was redesigned in [[2015]], it was fitted with a new movement, [[Lange L121|Cal. L121.1]].

===== See Also =====
  * [[Lange L095]] - The replacement movement for the Grand Lange 1
  * [[Lange L121]] - The replacement movement for the Lange 1
  * [[Lange L031]] - Second timezone movement for the Lange 1 Zeitzone
  * [[Lange L961]] - A derived tourbillon movement

<WRAP ud ud_mov>
**Manufacturer:**
  * [[A. Lange & Söhne]]

**Description:**
  * [[Manual winding]] movement
  * [[Shock protection]]
  * [[Escapement]] stone lever
  * [[Yoke winding system]]
  * [[Double barrel]]
  * [[Chaton|4 gold chatons]]

**Functions:**
  * [[Small seconds]]
  * [[Big date]], [[quickset date feature]]
  * [[Hacking seconds]]
  * [[Complication]] [[Power reserve indicator]]

**Data:**
  * 11½ [[ligne]]s
  * D 25.6 mm, H 4.6 mm
  * 53 [[jewels]]
  * 21,600 A/h
  * Power reserve 72 hours 

**Production period:**
  * Since [[1994]]
</WRAP>

{{tag>Movements Manual_winding_movements Double_barrel_movements A._Lange_&_Söhne_calibres}}