Scientific Radio System SR-25 manual

Folks,
I acquired a SR-MP-25 SRS radio and it seems it is not transmitting. I used H-80 mic, H-189 and H-250 handsets, nothing is transmitted. I am about to check the H-80 mic but suspect something is wrong with the unit. One H-80 came with the unit, I bought a NOS unit too and still nothing. I want to eliminate operator error. Does it have to have certain pins jumped or anything like that? I like the radio I would like to get it working. I am in Bay area, Northern CA;

Unit does receive well hence the issue is with transmission only.

THx,
Zee