Harassing telephone calls can unnerve a person, but most aren't as sinister as the receiver might suspect. Most come from telemarketers and their pesky computer dialers. To eliminate many of these calls, I suggest you sign up on the National Do Not Call List at: https://www.donotcall.gov.

The Ann Arbor Police Department receives many harassing telephone call complaints involving “hang up” calls. The vast majority aren't threatening. Usually, hang up calls are received either several times during the day or dozens of times during late night and early morning hours.

The daytime hang up call cases are usually caused by computers used by telemarketers. These computers automatically dial numbers and let the phone ring only three or four times. This is done because the computer doesn't want to be answered by an answering machine or voice mail. 

If a person answers one of these calls, the computer will alert that a human has answered, and a telemarketer is then supposed to pick up that line and perform the sales spiel. 

Many times, all sales representatives are busy when the computer connects with a person’s phone. That person hears only silence on the other end of the line. After saying “Hello” several times, the person will hang up. 

Since the computer registers a person (and not a machine) at that number, it will call the person again until there is a “successful” call. Telemarketers can now also call cell phones, so this phenomenon may also plague your cell phone.   

Numerous calls in the middle of the night can also be caused by telemarketers. The automatic dialers on fax machines for companies selling things (e.g. stocks or travel agencies selling trips) send special advertisements in the middle of the night to other fax lines. 

Sometimes, a citizen’s phone number is accidently entered as a fax line. When this occurs, the solicitor’s fax machine will call and chirp its fax mating call when a person answers. The solicitor’s fax machine regards the call as some sort of fax failure and will try again later.

About the time the person is falling back to sleep, the fax will call back to try connect with a fax machine again. These “fax mating” calls will continue from about five to 20 times through the night. Luckily, this type of telephone harassment is rare and easily remedied by calling the offending companies, who are usually very apologetic.

The calls to worry about are obscene phone calls, threatening telephone calls and continuing harassing calls when you can hear a person. These calls should be reported to the police and to your phone company. For more information about harassing phone calls a good resource is: http://www.privacyrights.org/fs/fs3-hrs2.htm.

Keep it locked, don’t leave it unattended, be aware and watch out for your neighbors.

Rich Kinsey is a retired Ann Arbor police detective sergeant who now blogs about crime and safety for AnnArbor.com.