What is difference between p17 p19 transducers

HI

Have an ST60 but moving to ng.

Am replacing the depth transducer - not sure what I have. Probably the P19. What is the difference between the P17 and P19?

I am connecting the new transducer through an ITC-5 to NMEA 2000 Raymarine SeaTalk ng Network and then to i70.

Thanks

Alan