On Call
On-call, or on-call scheduling, is a type of employee work schedule.
On Call may also refer to:

"On Call" (song), a 2007 song by Kings of Leon
On Call, a 1974 novel by Elizabeth Harrison (writer)
On Call: Serbisyong Totoo. Ngayon., a Philippine public service TV program
"On Call" (Casualty), a 2015 webisode of the BBC medical drama

See also
On-call room, a room in a hospital for staff rest
DART On-Call, a premium shuttle service by Dallas Area Rapid Transit