Clothing sensors are placed on garments using special prongs that are designed to avoid damaging the fabric. They are also designed to be difficult to remove without the proper tool, or without damaging the garment. Some clothing sensors contain a dye that will discharge if the sensor is removed without using the correct tool, ruining the garment for any would-be thieves. Others will emit a piercing alarm if the sensor is removed without the right tool.
In most systems, the monitors at the exit emit a signal that covers a small zone near the door. When a clothing sensor enters the area of the monitor, it either interrupts the signal, causing an alarm to sound, or it emits its own low signal that also causes the alarm to sound.
Removal of clothing sensors is specific to the type of sensor. One of the most common devices uses a powerful magnet. Others use a special key, and some use a combination of both. High-end clothing sensors require a removal device that not only uses a key, but must also activate a microchip before they can be removed.