In various embodiments, a rigid lens is attached to a light-emitting semiconductor die via a layer of encapsulant having a thickness insufficient to prevent propagation of thermal expansion mismatch-induced strain between the rigid lens and the semiconductor die. A predefined command sentence is provided representing at least a portion of a programming command, and includes words, which may be defined as constant or enterable words. 0% sulfated ash and a total base number of at least about 8. The lock member is provided with an engagement pin engageable with the engagement recess through a roller so that the first arm and the second arm are non-turnably locked. The timing recovery system in each receiver independently phase-aligns and frequency synchronizes the sampling signal to the serial data signal associated with the receiver. The users of the first type are in a condition to be provided said service only by means of said first set of resources, while the users of the second type are in a condition to be provided said service both by means of the first set of resources and by means of the second set of resources.