This International Standard specifies principles for the design and selection — independent of the nature of the energy source — of interlocking devices associated with guards.This International Standard covers the parts of guards which actuate interlocking devices.NOTE ISO 14120 specifies general requirements for the design and construction of guards provided primarily to protect persons from mechanical hazards. The processing of the signal from the interlocking device to stop and immobilize the machine is dealt with in ISO 13849-1 or IEC 62061.This International Standard does not necessarily provide all the specific requirements for trapped key systems. This International Standard provides measures to minimize defeat of interlocking devices in a reasonably foreseeable manner.