I recently had to add a cable box to my TV set up. I had one three years ago and I was able to use my VCR/DVD combo along with a A/B switch and program a recording on one station, and watch a different station while it was recording (w/o the A/B switch I was not able to) Then I got rid of the cable box (to save $) and three years went by. I do not remember the hookup order and when I went back to where I got the AB switch, they were stumped. I tried the one answer from Aug 2007 (augmentium), but it wouldn't tape a clear signal... it was all static when I tried to play it back. Please help! (so, I have a TV (older unit) Cable box, VCR/DVD combo, A/B switch, splitter)

I assume you went back to the cable box to get channels that your TV cannot get on its own (either premium channels, or channels your TV just can't tune to). That being the case, there will be some limitation in any setup you wind up with--you will not be able to simultaneously watch one premium channel and record another premium channel. You can watch premium or record premium, but not both at the same time. Generally, that is not too much of a restriction to live with.

Also, there are (at least) a couple of ways to hook up these components, each having different characteristics.
What would you rather do?

Be able to record "premium" channels
Be able to watch premium channels while recording normal channels

For #1, you would hook it up as shown in the first drawing.
Your TV tuner will be used to select the channel to watch when in the "A" position, and set to the output channel of your VCR when in the "B" position.
Your VCR will always be set to the channel that your cable box outputs.

For #2, you would hook it up as shown in the second drawing.
Your TV will always be set to whatever channel your cable box outputs when in "A" position, and set to whatever channel your VCR outputs when in the "B" position. (Note: if these can be the same channel, that simplifies things)

Now, use the following table to set the various components for your desired function:
Just watch TV (normal channels)
Hookup #1: Switch set to "A", TV selects channel to watch
Hookup #2: Switch set to "A", cable box selects channel to watch

Just watch TV (premium channels)
Hookup #1: Switch set to "B", cable box selects channel to watch, VCR on but not recording (could record this same channel, however)
Hookup #2: Switch set to "A", cable box selects channel to watch

Watch TV (normal channels), record (premium channels)
Hookup #1: Switch set to "A", TV selects channel to watch. Cable box selects channel to record.
Hookup #2: Cannot record premium channels

Watch TV (premium channels), record (normal channels)
Hookup #1: Cannot watch premium channels
Hookup #2: Switch set to "B", cable box selects channel to watch. VCR selects channel to record.

Note that "normal channels" may mean something different for your VCR than for your TV. If your TV is really old (i.e. not cable-ready) then, your VCR may be able to receive more channels than your TV. So, "normal" is dependent on whether your are trying to watch it or trying to record it.

I hope this helps,
WallyH