Abstract: In the present paper author has been consider a system which is having a special kind of k-out-of-n redundancy namely linear consecutive 2-ot-of-4: F system. These types of system have wide application in many industrial systems especially in medical equipment. Many medical diagnose equipment (one of the example is X-ray machines) having the linear consecutive k-out-of-n: F/G system. Basically a linear consecutive k-outof-n: G/F system is a system which work/failed if at least k consecutive components out of n components is working/failed. In the present paper one of the special cases of linear consecutive k-out-of-n: F system (by taking k=2, n=4) is investigated with the help of mathematical modelling and Markov process to find out its reliability characteristic. Critical units of the system are also obtained by sensitivity analysis.