Importance of transponder operation & altitude reporting. 
 Importance of transponder operation and altitude reporting 

 - [Washington, D.C.,  19--?]. 
 - v. 
<br/><br/> CRDP Program Historic Shelflist record. 
<br/><br/><label>Subjects--Topical Terms: </label><br/>Transponders.<br/>Airplanes--Radio equipment--Altitudes.
<br/><br/><label>Gov. Doc. Class. No.: </label>TD 4.8/5:91-50