when an interviewer asks what are 121 t/o mins

is it

2 engines or less 1 sm vis
more than 2 engines 1/2 sm vis

if weather is less than landing mins at departure airport then a t/o alternate must be filed with the requires mins for alternate distances

Depends on the company's ops specs. We can go down to 600rvr at my airline if runway lighting is sufficient.

in general, are these the mins they are asking for

In general, I'd say probably so.

T/O alternate mins do not include landing mins. T/O alternate mins, as already stated, are published in each airlines Ops Specs. Most are 600 RVR from what I've heard from freinds at other airlines, some are 500 RVR. The only time the T/O alternate comes into play is when the landing mins at the your departure airport are below landing mins. I guess what I'm trying to say is, 121 T/O mins have nothing to do with landing mins at that airport. T/O mins stand alone. And, you can only do the 600 RVR within certain crieteria, such as having RWY centerline lights.

Most companies are now authorized for and train/ check for 500 RVR take-off's.

The reason for this is that 500 RVR equals 150 meters. 150 meters is the minimum authorized take-off from foreign airports that measure in meters rather than feet. There are no airports in the US that allow for a take-off less than 600 RVR but we need to be authorized to 500 RVR to be able to to go down to 150 meters. RVR values this low only measure in even numbers such as 400, 600, 800, etc. therefore you will never see 500 RVR except in training or checkrides.

BTW: 600 RVR is 175 meters...

These are standard take-off minimums. If the airport has published take-off minimums that are greater than standard then you may not take-off below the published minimums.

According to the -9 for Memphis, runways 18R, 18C, 18L, 36R, 36C, and 36L have T/O mins of 5/5/5. I just saw this the other day and thought it was interesting.

Its not 5/5/5 if your ops specs say 6/6/6

So if the t/o mins on the plate are greater than what the op specs are, you follow the specs right?

say the departure says t/o mins are 800RVR and ops specs say 600RVR which one do you follow?