A DOORSTEP salesman, who targets elderly people, has been operating in Kirklees.
The man goes door-to- door trying to charge high prices for cheap CCTV systems.
He has been reported to have called at homes in Skelmanthorpe and Denby Dale.
Police say he has also tried to sell the systems in Wakefield.
A police spokesman said although some reputable companies did use a door-to-door sales service, people should still be wary.
He added: "Always ensure that the company is a member of a recognised body, and before agreeing to buy anything, always try to obtain at least three quotations from other companies in order to establish a fair price."
He said if people were suspicious they should call the police and not allow the salesman into their homes.