[BC] XLRs on the Ampex ATR

[PeterH5322]

>My recollection is that Ampex had a "standard" of pin 2 hot for microphone 
>inputs and pin 3 hot for line inputs.   Why??

There are two line input modes:

1) a balanced bridging input, in which a large balanced pad is placed in 
front of the microphone preamp, and the preamp is employed normally; this 
is non-inverting with respect to the Ampex standard, and

2) an unbalanced bridging unput, in which the pad, transformer, and 
preamp are bypassed; this is inverting with respect to the Ampex standard.