The emphasis on fixed service numbers includes the use of area codes so that the Number Plan is an open plan. Open Number plans are suited to environments where it is important or advantageous to contain the number of digits dialled e.g. as for electro-mechanical switching exchanges or there is a purpose to regional based management of telephony. The Lao PDR open plan using area codes has meant that local calling has required the caller to dial only the local subscriber number. This would have been advantageous in an era when most subscribers used mechanical dial phones (usually rotary dial), and the majority of traffic was local. Modern circumstances and looking forward neither of these preconditions would apply. Users are already dialling full length numbers for calls to mobile and WLL services