The oscillators in the array self-organize to form groups of phase synchronized clusters where each cluster is in perfect phase synchrony as a function of the coupling strength. Such a clustering is considered to be particularly significant in biological systems [@kaneko90; @sherman94; @strogatz93], in electro-chemical oscillators [@kiss02], etc. Recently, cluster synchronization in an array of three chaotic lasers without delay was reported [@terry99] as well. In our case, as the coupling strength increases, every individual system starts to drive the nearest system and the systems with small differences in their phases organize themselves to form small groups of clusters leaving the other oscillators with large phase differences to evolve independently. Further increase in the coupling strength results in an increase in the sizes of the clusters due to the locking of the phases of the nearby oscillators of the clusters for appropriate values of the coupling strength and finally ending up with large groups of clusters resulting in PPS (first order transition).

The paper is organized as follows: In Secs. \[sec:level2\] and \[sec:level3\], we will describe briefly the coupling configuration and the occurrence of global phase synchronization in an array of two different piecewise linear time-delay systems with open end 