About: http://webisa.webdatacommons.org/109404867

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	In one embodiment, the ringing signal is a 20 Hz, which implies a period of 50 milliseconds between ringing pulses.
http://www.w3.org/ns/prov#wasQuotedFrom	google.com