The Transportation Security Administration on Thursday unveiled new body scanners at Logan International Airport that will show only generic outlines of passengers instead of detailed images of their naked bodies.

Twenty-seven new machines, which use electromagnetic waves instead of X-rays, will replace all 17 old scanners that produced photo-negative-like images that were so explicit that they had to be viewed in private rooms by TSA officers. The older scanners have been used at Logan since 2010.

The new machines will project the same, “Gumby-type” image for each passenger, detecting weapons and other suspicious objects without revealing private parts, TSA officials said. Both TSA screeners and passengers will be able to see the images at checkpoints. “It’s just a continuation of the upgrading of our technology,” said George Naccara, the TSA federal security director at Logan.

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The new body scanners use an automatic threat detection system that only generates an image if it detects an anomaly, such as a wrist watch or a powdered explosive. If nothing is found, the word “OK” will appear on a green screen. The process will also be quicker, Naccara said, taking three to five seconds instead of the 16 to 18 seconds that the old machines required.

If the machine detects something out of the ordinary, officers give the person a pat down.

In all, the TSA has installed 730 body scanners at more than 190 airports around the country—555 of which use the new software with the generic body outline.

At Logan, all 27 machines will be installed by mid-November at each of the airport’s 10 checkpoints. The old machines will be repurposed at other airports. Eventually, Naccara said, fewer machines will be needed as more travelers enroll in the TSA’s expedited screening program.