Abstract: An array of light emitting devices, each device comprising a sloped wall mesa (24) of luminescent semiconductor material. Extending over the sloped wall mesas (24) is a metal contact (30). The array can be arranged as a parallel addressable system so that all devices (24) can be stimulated to emit light simultaneously. Alternatively, the array can be arranged as a matrix addressable array, in which case individual devices can be selectively stimulated.

Abstract: In order that emergency service vehicles can be dispatched to the correct destination promptly, accurate information about the location of the caller is needed. Another problem concerns routing emergency calls to the correct destination. For emergency calls a universal code is used such as 911 in North America and 112 in Europe. This universal code cannot be used to identify the destination of the call. These problems are particularly acute for nomadic communications systems such as voice over internet protocol communications networks. That is because user terminals change network location. These problems are solved by enabling the geographical location of the emergency caller to be determined by entities within a packet-based network without the need for modification of existing emergency services network infrastructure.