Does a DE9 connector use all 9 pins?

Each pin are assigned a name that carry a specific signal which are: CD, Rx, Tx, RTS, GND, DSR, RTS, CTS, & RI. Most common application only uses Tx, Rx,& GND (pins 2, 3 & 5) and the rest are left unconnected (NC). Try searching DB-9 instead. DE-9 (which is the right name) almost always been called DB-9 (a misnomer but wide accepted). hopes that helps.