A US woman who dialled emergency services as her baby choked was given life-saving advice from her phone operator husband who answered the call.

Janna Scott from Washington State immediately recognised her husband Chris's voice when he answered the 911 call, local TV station KING5 reported.

Mr Scott was able to remain calm and help his wife save their six-month-old son Jacob, who was unconscious and not breathing.

"Chris, he's choking on something," Mrs Scott said after he answered the call.

"Who is?" he replied, not realising Mrs Scott was talking about their son.

Maintaining his composure in the extraordinary circumstances, Mr Scott, who is still a trainee emergency phone operator, directed his wife on how to clear the baby's airways with a series of strikes to his back.

"Take a deep breath I know it's really scary right now," Mr Scott told his wife after Jacob began breathing again.

Mr Scott began his training recently after returning home from a tour of duty in Iraq as a marine reservist.

"It was really good for me to have him on the line," Mrs Scott said after the incident.

"I trust him, because I know he knows what he's doing."

Mr Scott's supervisor sent him home to be with his family after the incident.