Studies an aspect of detection and isolation delays which has been ignored in many papers in this area. Surprising since it is highly relevant from a practical point of view. In continuous-time systems this is not a serious matter since we can always guarantee an arbitrary small delay and nearly all designs in the literature yield this arbitrary small delay. However, for discrete-time systems the situation is different and by designing specifically to reduce the detection or isolation delay we can get better results compared to most designs as available in the literature