The invention concerns an assembly comprising a flying balloon and a tower. The apparatus operates in a benchmark mode to determine benchmark duty cycle information and then subsequently operates an a relative mode to determine relative duty cycle information of the clock signal at a selected node in comparison to the clock signal at an external input node. A communications interface arranged to communicate push-to data packets, originating from a push-to client participating in a push-to user group comprising at least two push-to clients, from a push-to server to a broadcast node arranged to broadcast the push-to data packets to broadcasting clients which are not part of the push-to user group is also disclosed. The axial index of refraction variation may be discrete or may be an axial gradient index variation. An obstruction structure is coupled to move relative to the opto-interrupt sensor when the media guide is translated and provides one or more fins to selectively block or open the optical signal path of the opto-interrupt sensor, with the sensed media width being determined according to the output signals of the opto-interrupt sensor and the potentiometer.