Q: How does a PLB compare to an EPIRB?
A: The following are the most noticeable and critical differences:
* An EPIRB is bulky and much larger; a PLB is "pocket-sized"
* An EPIRB is designed to operate while floating with the antenna in a transmitting orientation; a PLB is not required to float. Some PLBs do float, but they do not maintain the antenna in a transmitting orientation, it is simply a means to prevent loss by sinking.
* An EPIRB is equipped with a strobe light; a PLB does not have a strobe light
* An EPIRB is equipped with a tether to attach it to the vessel or life raft; a PLB is not required to have a tether, though all have either a wrist strap or some sort of short tether.
* Some EPIRBs are automatically deployed and activated if a vessel sinks (Category 1), others are manually deployed and activated (Category 2); a PLB can only be manually deployed and activated.
* An EPIRB is required to transmit a minimum of 48 hours at -40°C/F; a PLB is required to transmit a minimum of 24 hours at either -40°C/F (Class 1) or -20°C / -4°F (Class 2).
* An EPIRB has a 100 milliwatt 121.5 MHz homing signal; a PLB homer is 25 milliwatts. The practical difference is not significant since the 406 MHz based location information gets any searchers close enough that the lower-powered homing signal is perfectly adequate.
* An EPIRB is technically for use in a marine environment; a PLB can be used anywhere.
* An EPIRB alert is routed automatically to the Coast Guard; a PLB alert is routed first to the Air Force Rescue Coordination Center and it then routed depending upon location or other information and a marine alert may take up to 90 minutes, worse case, to be transferred to the Coast Guard. If there is a GPS location it will be routed directly to the Coast Guard by the computer and if other information from the Emergency Contacts indicates a marine alert it will be routed quicker. Authorities are working on a system to allow quicker response to PLB alerts in the marine environment.