How to identify COS, PTT, TX and RX on radio?

Hi!

I have a Puxing 888K that I want to connect to a CM108 fob for a new node. I have found the schematics online but lack the knowledge of identifying COS, PTT and where I should take TX and RX from.

Internally it is very different from Baofeng which is well documented.

How can I test which points I can use for these connections for best performance. What should I look for on my multimeter?

Any assistance would be greatly appreciated.

Regards,
Adam

puxing_px-888_vhf_sm.pdf (1.1 MB)

Could it be from one of the sections given below?