To enable the tamper output on an M3-MIFARE-EM, the following steps must be followed:
1. Activate the tamper alarm function. To do this we have to access the menu of the device and put the following sequence:
* 0 # 1 2 3 4 5 # 7 1 #
2. When we jump the tamper, the tamper output (pink cable) next to the positive power supply of the device will take 12V. (see diagram below)