Constantin:
No no, I meant insulated, not isolated. my bad. I will go back and correct that. I had meant to use this power switch tail that uses a triac to turn on and off the power supply to the DVR. Does that make more sense? Apologies again for the typo.
Those 'power tail' products generally do use isolated input via a opto-isolator input device. I base this on the spec for it's controlling input requirement, ( DC input: 3-12vdc (3-30ma), terminal block accepts #14-30 AWG wire) which is common for opto-isolated device that use an led as the interface connection to the microcontroller. However the standard power tail does automatic zero crossing turn-on and you have no control to say turn the tail off for just one AC (or one half) cycle. They do sell a product called the Zero cross tail ( http://www.powerswitchtail.com/Pages/ZeroCrossTail.aspx ) which can provide a timing signal that one could use to control the timing of the power tail such that one could probably create single cycle drop outs.
As far as the how any given device will respond to short AC drop outs really depends on it's internal DC power supply design the device is using , how much main DC filtering capacitance reserve the supply has and of course the current draw requirements of the device.
All in all this seems to be a demanding test/analysis effort and you really have to have a detailed specification requirement to test against.