RF from MTS box through SC box, through VCR, to TV.
A/V from MTS box to VCR, to record when watching SC, with VCR in TV mode.
RF from MTS box, through VCR, through SC box, to TV. A/V from SC box to VCR. Use bypass on SC box to view VCR or MTS. You can record SC from A/V in, and bypass VCR and SC box to view MTS.
Or get a good remote controlled RF-A/V switch.