[MFJ-Ameritron] MFJ-493

[Charles Ring]

I just bought a used MFJ-493 keyer, by far the most sophisticated I have 
any experience with. The manual says it ha separate keying outputs for 
positive and negative transmitter keying lines but I see only one, with 
an RCA jack. Where is the other one and which is which?

What is the voltage and current limit of each keying output?

The page in the manual marked "schematic" is blank.

*Charles Ring W3NU*