[RTTY] Help With Dovetron TU's

[bmarx at bellsouth.net (Bill Marx)]

Can someone please tell me the difference between these Dovetron TU's? Cannot 
find any info on them. Is there information on a site
somewhere? Why would one be better than the other.  Or are they all good to 
work with?

DOVETRON MPC-1000TII MILITARY CV3883/UG

Dovetron MPC-1000RII regenerative RTTY terminal unit.

Dovetron MPC-1000R RTTY terminal unit

The first two look alike but can find no information. I know the third uses a 
CRT but need more information.

Bill Marx W2CQ