relaying data transmitted at other wireless transceivers at for example 50 to 100 foot intervals the wireless mesh network can also be used to relay two way voice communications in order to overcome a common problem of a structure physically interfering with or blocking normal direct radio communication systems utilized by fire department personnel this physical interference may occur in the following examples reinforced concrete structures certain metal framed structures underground and subterranean structures or other types of structures which are known to block normal direct radio communications the amount of light emitted from the leds 112 or the number of leds 112 energized is in accordance with some embodiments calibrated and sequenced to produce a visual indication of an actual flow rate of fluid within axial flow channel 612 by way of example a red illuminated egress arrow 114 may be illuminated indicating a dangerously low rate of water flow from zero to 50 gallons per minute fig1 a a yellow illuminated egress arrow 114 may be illuminated indicating a low rate of flow requiring caution on the part of the operator of 51 to 100 gallons per minute and a green illuminated egress arrow 114 may be illuminated indicating a safe flow rate of 100 plus gallons per minute multi color leds 112 for example can be employed to emit red light yellow light and green light from the same leds 112 as a function of how the leds 112 are energized e g by positive e g red or negative e g green dc current or ac current e g yellow in addition the red and yellow egress arrows may also flash on and off at a varying interval in order to further.