1. Tell-tales and indicators need not be visible nor recognisable when not activated.

2. Blab (third-person singular simple present Blabs, present participle Blabbing, simple past and past participle Blabbed) ( transitive , intransitive ) To tell tales; to gossip without reserve or discretion.

3. whereas account should be taken of the new identification techniques which should enter into widespread use, consisting of the use of words or abbreviations instead of symbols for controls, tell-tales and indicators