About: http://webisa.webdatacommons.org/234998720

Property	Value
http://www.w3.org/1999/02/22-rdf-syntax-ns#type	http://www.w3.org/ns/prov#Entity
http://www.w3.org/ns/prov#value	Typically, one of the signals is fixed very high up on a mast and the other one much lower down, so that one or the other is always in view from all positions along the tracks as it is approached.
http://www.w3.org/ns/prov#wasQuotedFrom	irfca.org