When Mrs Boon Hui Seng signed up for the Singapore Armed Forces Volunteer Corps (SAFVC) in 2016, she was close to 45 years old, the maximum age for applicants.

Mrs Boon, a former Chinese language teacher at a secondary school, wanted to learn more about national defence and also to push her own physical limits.

Now 47, she was one of the oldest in her March 2016 basic training cohort.

In its first year, in 2015, the SAFVC enlisted 226 volunteers and it has since trained more than 700, who serve alongside active and national servicemen in the Singapore Armed Forces.

"It is heartening to see more Singaporeans and permanent residents stepping forward to contribute to national defence and support national service," said Senior Minister of State for Defence and Foreign Affairs Maliki Osman at a promotion and formation patch presentation parade at Maju Camp yesterday.

"SAFVC continues to attract quality and diverse... volunteers who hail from a wide range of backgrounds and experiences."

Singaporean women, first-generation permanent residents and new citizens can sign up to join the SAFVC as long as they are between 18 and 45 years old, are physically fit and have a desire to contribute to national defence.

Before serving in their assigned roles, these volunteers have to undergo two weeks of basic training to adapt to the military regimentation, learn to fire an SAR-21 rifle, operate as a team during a field camp, and understand the importance of national defence.

And before the volunteers can be deployed, they spend one week on qualification training and one week on advanced training to acquire additional skills.

The volunteers, who can be called up for deployment for up to 14 days annually, serve in various roles across the army, air force and navy.

The SAFVC has more than 70 bridge watchkeepers, whose duties on a ship include looking out for potential hazards, other vessels and navigation marks around the ship in two-hour shifts.

On June 5, Mrs Boon, who has a 14-year-old daughter, joined six other volunteers as bridge watchkeepers on the RSS Persistence, which was taking part in an exercise.

Lieutenant-Colonel Gary Ow, commanding officer of the RSS Persistence, said volunteers like Mrs Boon play a vital supporting role in the navy as "no person has the resources to manage the whole ship".

He said he demands the same standard of work from the volunteers as from other crew members.

"I don't think it is an easy task. I salute them because they actually don't have to do this," he added.