The CAB-1 is the TMCC controller from 1995 ( http://www.lionel.com/products...ote-control-6-12868/ )- you probably do not want to invest in this old technology. The CAB-1 will also require a TMCC Base ( http://www.lionel.com/products...ommand-base-6-12911/  
The CAB-1L is the logical Legacy successor of the CAB-1 design. It exposes most of the TMCC operations and some of the Legacy operations available ( http://www.lionel.com/products...e-controller-6-37155 ). The CAB-1L will require a Legacy Base #992 (Only available with the CAB-2 http://www.lionel.com/products...-command-set-6-14295) or a BASE-1L ( http://www.lionel.com/products...trol-base-1l-6-37156 ), or the CAB-1L and BASE-1L can be purchased as a set ( http://www.lionel.com/products...-command-set-6-37147 ).
If you are serious about command controlled trains, I would buy once, cry once with the #990 (The #991 CAB-2 remove and #992 Legacy Base Package http://www.lionel.com/products...-command-set-6-14295 )