JP 3-50 National Search and Rescue Manual Vol I - US Navy

failure, and Code 7500 an unlawful interference with the aircraft. When
no other code is assigned, Air Force and Coast Guard aircraft are
authorized to use Mode 3, Code 1277 in domestic airspace, on official
SAR missions, and en route to or within an assigned search area.
315 EPIRB and ELT
The Emergency Position Indicating Radio Beacon (EPIRB) and the
Emergency Locator Transmitter (ELT) are small emergency radios that may
be fully automatic, semi-automatic, or hand activated. They may be
transmitters only, transceivers, beacons only, or a combination. The
various types are described below.
A. EPIRBs are passive devices for transmitting maritime distress
alerts. Six classes of EPIRBs are currently in use by United States
vessels:
1. Class A EPIRBs operate on 121.5 and 243 MHz and are
automatically activated. They are now carried aboard all
Coast Guard vessels of the WPB class and larger, and are
required on all vessels inspected for ocean and coastal trade
whose route extends more than 20 miles from a harbor of safe
refuge. They transmit for at least 48 hours.
2. Class B EPIRBs operate on 121.5 and 243 MHz and are manually
activated. Their use is voluntary for uninspected vessels,
but all vessels which travel more than 20 miles offshore are
encouraged to carry either Class A or Class B EPIRBs. They
transmit for at least 48 hours.
3. Class C EPIRBs operate on VHF/FM. They transmit a 1.5-second
alert signal on channel 16 (156.80 MHz) to call attention to a
distress, then transmit a 15-second locating signal on channel
15 (156.75) to allow homing. Both signals repeat
periodically, and are designed after the international twotone
alarm signal. They automatically transmit for 24 hours
and then shut off. They can then be manually reactivated.
4. Class S EPIRBs operate on 121.5 and 243 MHz and are used in
survival craft. These EPIRBs can be automatically or manually
activated and (optionally) be required to float. These EPIRBs
may provide either continuous or intermittent operation. If
intermittent, the duty cycle is 50 percent for a 2 minute
period.
5. Category I 406 MHz Satellite EPIRBS are automatically
activated, float free devices operating in the 406 MHz band
internationally allocated for satellite EPIRBs. These devices
are coded with vessel information and when activated, this
coded information will be transmitted via the satellite system
to the appropriate RCCs. These devices provide accurate
location information worldwide. Similar to Class A EPIRBs in
usage, SOLAS and other classes of vessels (e.g. fishing