ELT(Emergency Locator Transmitter) 应急定位发射机，也称应急电台，分便携式和机载固定式两种类型。一般来说，便携式在左后乘务员座椅后面，但是有时候我们也可以在飞机前部行李架看到它。机载的一般位于后乘务员站位头顶板附近。民航应急定位发射机工作频率为121.5MHz、243MHz和406-406.1MHz。121.5MHz频率，供使用117.975MHz至137MHz频带内的航空移动业务电台进行遇险和安全无线电话的通信。还可用于营救器电台和应急示位无线电信标电台。
243MHz频率，供营救器电台使用的频率。可用于有人驾驶空间飞行器的搜索和救援工作。406-406.1MHz频带，是卫星应急示位无线电信标地对空方向的专用频带。

AK-451系列应急定位发射机的特点：

1.Applicable to all Land Uses, Hiking, Camping, Skiing, etc.

2.Harsh/ Robust/ Heavy Duty PLB. Survival tested at 500G Shock; 1000G Crush.

3.Ultra Long lasting Battery Package, up to 78 hours @ -20 deg C, end of 5 years life, 10 years storage life time. Lithium type, LiMnO2, 4 D-Size.

4.Dimension and Weight: (4.27”L x 2.95”W x 5.64”H), 1lb 8 oz

5.Simple operations

6.Protocol: Coding Programming International Worldwide, all available PLB Protocols, i.e. Long and Short Messages (User / User Location / Standard Location/ National Location) PLB w Serial No.

7.OXCO conventional technology for perfect gradient temp stability.

8.PERP: 5W+/-2 dB @ 406.028 MHz for 24Hrs

9.PEIRP: (14-20) dBm @ 243 & 121.5 MHz for 78 Hrs @-20 deg C, end of life.

10.Waterproof and Flame tested.

11.Type Approvals: COSPAS-SARSAT, FCC.

12.Patent Pending. Made in U.S.A.

13.WARRANTY:Two (2) years. Optional extended Five (5) years Warranty

AK-451系列应急定位发射机的型号：

AK-451-0 ELT Transmitter only........................................................................

AK-451-1 General Aviation.............Whip / USA..............................................

AK-451-2 General Aviation.............Whip / Portable / USA, Triple Freq............

AK-451-2D General Aviation.............Whip / Portable / USA, Dual Freq.............

AK-451-2D-GPS General Aviation......GPS / Whip / Portable / USA, Dual Freq...

AK-451-3 Business Jet Aircraft......Rod3 / Portable.........................................

AK-451-4 Business Jet Aircraft......Rod4 / Portable.........................................

AK-451-5 Transport Aircraft...........Blade / Portable........................................

AK-451-6 Transport Aircraft...........GPS / Whip / Portable...............................

AK-451-7 Business Jet Aircraft......GPS / Rod3 / Portable..............................

AK-451-8 Business Jet Aircraft......GPS / Rod4 / Portable..............................

AK-451-9 Transport Aircraft...........GPS / Blade / Portable..............................

AK-451-10 General Aviation.............Auto Portable............................................

AK-451-11 All...................................Survival.....................................................

AK-451-12 Helicopter.......................Heli /w 450000-1 / Whip / Portable............

AK-451-13 Helicopter.......................GPS / Heli / 450000-1 / Rod3 / Portable...

AK-451-14 Helicopter.......................Heli / Rod3 / Portable................................

AK-451-15 Helicopter.......................Heli / Whip / Portable................................

AK-451-16 Helicopter.......................Heli /w 450000-1 / Rod3 / Portable...........

AK-451-17 Helicopter.......................GPS / Heli / Whip / Portable......................

AK-451-18 Helicopter.......................GPS / Heli / Rod3 / Portable.....................

AK-451-19 Helicopter.......................GPS / Heli / 450000-1 / Whip / Portable....

AK-451-20 General Aviation.............Whip / Portable / Canada..........................

AK-451-21 General Aviation.............Whip / Portable / International……………..

AK-451-22 (Reserved)
AK-451-23 General Aviation.............GPS / Whip / Portable...............................

AK-451-23D General Aviation.............GPS / Whip / Portable...............................

AK-451-24 (Reserved)
AK-451-25 (Reserved)
AK-451-RK1-C General Aviation................Whip / Portable....................

AK-451-RK1A-C Business Jet Aircraft..........Rod3 / Portable....................

AK-451-RK1-GPS-C General Aviation................GPS / Whip / Portable.........

AK-451-RK1A-GPS-C Business Jet Aircraft..........GPS / Rod3 / Portable.........

AK-451-RK2-C Transport Aircraft...............Blade / Portable...................

AK-451-RK2-GPS-C Transport Aircraft...............GPS / Blade / Portable........

 AK-451系列应急定位发射机的使用机型清单：