NOVELTY - The electronic key comprises a housing (11) in which an electronic and an electric battery are arranged for the remote control and also an emergency key (30) for a mechanical actuation of the closing system in an emergency, a locking device between the emergency key and the housing for position security of the emergency key during non-use, and a detachable cover (36) at an external area of the housing. The cover locks in fixing condition of an opening (15) in the housing and accessibly makes in released state of the housing inside through the housing opening.    USE - Electronic key for remote-controlled closing system in a vehicle.    ADVANTAGE - The electronic key has good reliability and is easy to install.    DETAILED DESCRIPTION - The electronic key comprises a housing (11) in which an electronic and an electric battery are arranged for the remote control and also an emergency key (30) for a mechanical actuation of the closing system in an emergency, a locking device between the emergency key and the housing for position security of the emergency key during non-use, and a detachable cover (36) at an external area of the housing. The cover locks in fixing condition of an opening (15) in the housing and accessibly makes in released state of the housing inside through the housing opening. The cover forms a preassembled unit together with the emergency key against the housing. The preassembled unit locks in its installation position in the housing of the housing opening and release in its extension position. A locking device (46) serves for the emergency key for securing the installation position of the entire preassembled unit in the housing and secures the cover formed by the preassembled unit in its mounting condition in the housing opening. The emergency key comprises a key head serving to its handling and a key shaft with a mechanical encoding. The two-piece locking device consists of a manually operatable active locking part and a non-operatable passive counter locking part. The active locking part is arranged in the key head of the emergency key during the passive counter locking part exists itself in the housing. The key head comprises a handle for active and/or inactive position of the locking device. The handle of the locking device in the installation position of the preassembled unit is accessible from the external side of the preassembled unit. In the installation condition of the preassembled unit, the top of the cover and the show side of the key head forms a cover function for the housing opening. The cover produced from the preassembled unit possesses a holding fixture for the key shaft of the emergency key in which the key shaft is pluggable. In the installation position of the preassembled unit and in the protection position of the emergency key, wide area of the key head comes to lie next to the top of the cover. The cover is formed as flat sheath, which has an inlet slot at its sheath end turned towards the key head. The inlet slot serves for putting away the key shaft of the emergency key. The protection position of the emergency key functions the sheath inside as boiler for the key shaft. The key head locks in the installation position in the housing of the inlet slot of the sheath. The housing has an open channel in the area of its external surface. The channel in the installation position appliques the preassembled unit and then the cover/sheath and the key head lie in the channel. The installation position is secured by detent means that are arranged complementary to each other between the cover sheath and the housing channel. The preassembled unit passes through a defined multi-phase sort out movement during transition between the installation position and demounting position. The housing-/channel opening comprises an indentation in its opening end. The accompanying end of the installation unit possesses a recess that grips in the installation position during the first or last phase during the inlet and outlet component of the indentation. The channel possesses an open channel inlet at the front side of the housing end. The key head locks with its external front area of the channel inlet in the installation position. After the passive position of the locking device, the key head of the emergency key is unplugged in a further phase of the putting movement from its protection position in the cover/sheath with a subsection of the key shaft in a delivering position, where it juts out from the channel inlet. The key emergency in the notification phase of the sort out movement serves from its delivering position as lever arm for pivoting out the preassembled unit from the housing-/channel opening. The opening end of the open channel inlet faces from the housing. The indentation appears on the housing-/channel opening on the one hand and the recess on the cover/sheath on the other hand as swivel joint during pivoting out of the preassembled unit from the housing. The preassembled unit in the installation position covers a chamber in the housing inside in which the electric battery is arranged for the remote control. In the extension position, the battery is accessible and interchangeable in the housing interior. The preassembled unit has a pressing profile in its lower side turned towards the housing interiors for the position security of the electronics or the battery. The preassembled unit compresses an elastomeric sealing present in its installation position. The active locking part of the locking device and/or its handle are arranged on cover/sheath of the installation unit. The housing comprises a test field on its external surface for manual activity of the remote control.    DESCRIPTION OF DRAWING(S) - The figure shows a longitudinal section of an electronic key.    Housing (11)    Housing opening (15)    Emergency key (30)    Detachable cover (36)    Locking device. (46)