[TenTec] Dumb Question

[BPCI at aol.com]

Warning - This is a dumb question. 
 
I have a Century-21 that I keep mostly for playing with occassionally. I  
keep seeing crystal callibrators advertised for it. What is a crystal  
callibrator, and do I need one for my C-21 for my occassional QSO's with this  fine 
sounding radio? Thanks to all who take time to respond...73, Ci

 
Ci Jones,  WU7R
FISTS #10789, CC #1853
NAQCC #306
ARCI #12163
SKCC #22,  C#38
FP #1442