Ptt

Initialism of

trainer.

Initialism of

and telegraph.

Initialism of

transmitter.

Initialism of Partitioning

test.

Initialism of

time.

Initialism of polytrimethylene terephthalate.

Initialism of

test.

Initialism of part

(See Flight

at Wikipedia).

Initialism of push-to-talk / press-to-talk / push-to-transmit / press-to-transmit.