In all systems the homing head has to remain stabilised in space during a period when there is no guidance signal . 在所有系统中，当没有任何制导信号时，导引头必须在空间保持稳定。
2.
Instrument landing system ( ils ) a standard icao precision landing aid to provide accurate azimuth and descent guidance signals for use by aircraft for landing on the runway under adverse weather conditions 这是国际民航组织指定的标准精确著陆导向设备，提供准确的方向指示及下降指引讯号，即使在恶劣的天气状况下，航机亦能安全地在跑道上降落。
3.
An ils is a standard international civil aviation organisation ( icao ) precision landing aid provides accurate azimuth and descent guidance signals for use by aircraft for landing on the runway even under adverse weather conditions 这是国际民航组织指定的标准精确著陆导向设备，提供准确的方向指示及下降指引讯号，令航机即使在恶劣的天气状况下，亦能安全地在跑道上降落。
