J430
I have since been informed they have a life span of 3 - 5 years, unlucky me , but it makes you think very hard about the fact that most older GA aircraft (and some no so old) probably have deffective encoders, that only get checked every two years (hopefully) and their Transponders do not have a display for the PA being transmitted.
A point that has been studiously avoided by the protagonists here on this and the TCAS debate.
Jerricho