A conventional keyless entry system uses a radio wave as an unlocking or locking signal and is therefore substantially non-directional. For example, when an unlocking operation is performed, keys of all doors are unlocked, so that for example in a vehicle having a certain slide door or a kick-up door, an occupant of the vehicle may forget to lock the door. According to the presently disclosed subject matter a keyless entry system for locking and unlocking lock(s) of a vehicle can include an infrared light projector having a narrow radiation angle, and a light receiving/emitting unit corresponding to operating conditions of keys/locks. The light receiving/emitting unit can include a combination of a light receiving element for receiving the infrared light and a light emitting element for indicating the position of a key/lock which is operated correspondingly to the infrared light received by the light receiving element. Thus, among other features, locking and unlocking of only a requested door by means of the narrow radiation angle can be accomplished.