This figure is more than double the 19 cases in 2004. In 2005, 35 cases were dealt with. Some of those who were eventually taken to court were jailed, while others were fined.

The latest known case was less than two weeks ago, when a man was arrested on Sept 26, after he allegedly made obscene calls in Hokkien to the police.

The 43-year-old, a part- time waiter, is believed to have used a pay phone to carry out the act in the early morning, and is suspected of having made numerous calls since July.

He has been charged and is under remand at the Institute of Mental Health.

Deputy Superintendent Tang Soon Teck, officer commanding of the police's radio division, said the heightened enforcement was necessary, especially in the face of 'serious' prank calls like bomb hoaxes.

Nuisance calls to the 999 hotline have been described as a 'perennial problem' for the police. Seven in 10 calls in the past three years were nuisance calls.

Of the total 5.1 million calls made to the emergency number in the past three years, a staggering 3.5 million were prank calls, according to police statistics.

This means that just about three in every 10 calls made to the police operators were genuine.

There was no let-up last year - 1.1 million of the 1.6 million calls, or 68.8 per cent, were nuisance calls.

Said DSP Tang: 'They prevent us from attending to genuine calls for which every minute can make the difference between life and death.'

Anyone making calls to an emergency number with the intention to harass, faces up to a year's jail, or a fine, or both.

Not everyone is hauled to court. Among the nuisance callers are the mentally unstable. There are also children, who were linked to about one in five prank calls in 2004 and 2005.

This proportion, however, dropped to about 8.3 per cent of all nuisance calls last year.

This could be because police officers have been visiting primary schools to give talks.

DSP Tang told The Straits Times of another new move to tackle nuisance callers: The creation of posters pitched at children and also the larger public, which will be unveiled by the end of the year.

Senior Staff Sergeant Kartini Keman, a hotline deputy team leader who has been at her job for 11 years, knows well how some children can end up being mischievous.

'I tell them firmly not to play with the phone,' she said, adding that, sometimes, officers redial the numbers and speak with the children's parents and guardians.

The police also routinely issue advice or warning letters to nuisance callers, with an average of 6,300 letters sent out in each of the past three years.

Even some genuine calls should not be an emergency one. Some people mistakenly call the police for matters unrelated to police work. An estimated four in 10 genuine calls are 'peripheral' calls of this type.

To reduce the number of such calls, a website will be launched by the end of the year. It will advise the public when to call the police hotline and when to contact other government agencies for help.

The website will list details of these agencies and their hotline numbers, along with the issues under their charge.

Despite the thousands of calls handled every day, DSP Tang said his officers have been able to uphold the police's service pledge, which says that calls have to be answered within 10 seconds, 90 per cent of the time.

'We constantly upgrade our system...and we have visited other forces overseas - the technology is there,' he said.

joolin@sph.com.sg