Enhanced CCTV, comprising speakers mounted near pre-existing cameras, will allow control room operators to verbally warn anyone they spot misbehaving in certain areas of the town centre.
Although the scheme will try to stamp out littering and other minor anti-social behaviour, Brendan Glynane (Lib Dem, Far Cotton) said the most significant side-effect will be to stop serious violence at night.
He said: "I think a lot has been said about the littering side of these systems but it will make thousands of people coming into town to have a good time each weekend feel a lot safer.
"They will give people more confidence in CCTV by showing the public there are actually people being monitored.
"If it stops one fight degenerating into something worse and saves one life it will have been money well spent."
Councillor Glynane started the first automated message – recorded by Northants 96 DJs Jagger and Woody – to shoppers in Abington Street yesterday morning by pressing the button at the St John's control centre.
The cameras will cover the areas favoured by night-time revellers like Abington Street, Bridge Street and The Drapery.
Debbie Ferguson, Northampton Borough Council community safety manager, said she was sure the new speaker system would help police deter crime.
She said: "Prevention is the principal aim of the scheme. If someone is committing a crime or behaving anti-socially and they are told they are being monitored, it is likely they will stop what they are doing.
"It is about challenging unacceptable behaviour and making people think twice.
It is not a substitute for policing and it won't solve everything, but it is another tool we can use to help us make Northampton safer and tidier."
The day was also an opportunity to present awards to Northampton schoolchildren who were judged winners of the It's Not Okay to Drop Litter poster competition.
Rani Isaac, aged 13, of Thomas Becket Catholic School, said: "I thought my cartoon design would stick in people's minds.
"I like the idea of CCTV talking to people and I think it will make people who drop litter think twice."
nick.spoors@northantsnews.co.uk