When three armed men led police on a chase that ended violently in a Malden parking lot last month, public safety officials used a reverse 911 system to alert residents to the commotion.
Now planners are calling for wider participation in the program, called Code Red, asking people to sign up online to verify their phone numbers.
"This system is only as good as the telephone database supporting it," the city said in a statement. "If your phone number is not in the database, you will not be called."
Businesses as well as individual households are encouraged to register, and the system is compatible with cellphones and land lines.
To register without using the Internet, send a letter with contact information to:
Ron Cochran in the office of Mayor Gary Christenson, 200 Pleasant St. Malden MA 02148.