Having read about their existence in the Time-Life book "Russia Beseiged", I was curious to know more about them. Is it safe to assume the defense systems consisted of whatever weapons could be rescued from the field and placed in whatever suitable nooks and crannies the town or village offered?

And another thing-in the extreme cold, how was anybody able to get these weapons to work? And presumably supplies were airdropped in to get them through the winter?