It seems that you want to know how to connect two Closed-circuit television (CCTV) cameras to your Slingbox PRO-HD.
If you check the Slingbox PRO-HD back panel, you will notice that the Slingbox PRO-HD has only one set of Composite inputs (yellow). This means that if you want to connect another camera, you will need to use either a Component (RGB) or S-Video cable. Keep in mind that the Slingbox will recognize the CCTV camera(s) as any other AV source.
Hope this helps!