A reader from Silver Spring writes that she often goes to visit her parents at their "lovely high-rise apartment." The building has one of those buzz-in security systems -- the kind where you look up the apartment number on a board in the lobby and dial a two-digit code number on a nearby house phone.

Supposedly, with the aid of this system, a tenant can admit those visitors he wants to admit and keep out those he wants to keep out. "But when I visit my parents, I rarely use the security system," my reader writes. The reason: she gets in without it.

"Outgoing tenants smilingly open the lobby door for me," she says. "Incoming tenants who have keys, of course smilingly unlock the lobby doors for me. The visitor in front of me phones a tenant, the lobby door is unlocked, and the visitor smilingly holds the door open for me.

"These people don't know me from Adam!" my reader says. " . . . . Would it be more expedient to install another type of security system?"

It sure would, dear reader, and the new system should be exactly what it used to be: a living, breathing, non-napping human being sitting at a desk and calling upstairs to clear each visitor.

But that system got flattened years ago by Bottom Line Disease. Apartment managements discovered that you don't have to give a board and a phone Thanksgiving Day off. To dump humanity and install automation seemed, in dollars-and-cents terms, an obvious move.

But the police will tell you that most apartment burglaries and con games are carried out by people who gain admission to buildings through the "coattails" system my reader describes.

Even deliveries that seem legitimate might not be. Reader Rachel Kopel loves to frequent thrift shops. She points out that, for very few nickels, you can buy a shirt at a thrift shop with a company name-patch on one breast and JOE on the other. Just like that, you look as authentic as Mr. Goodwrench or the man from Pepco. What spoilsport wouldn't open a buzz-in door for you?

Isn't it time for managements to spring for real live desk clerks? And while we wait for the powers to see the light, isn't it time for residents of buildings with buzz-in systems to be a lot more careful about bestowing free entry upon strangers?