The thoughts behind this fence were that we needed to slow the foxes' passage through the fence so that ideally, it would receive at least two electric pulses.
The problem is always exacerbated by undulating country, so post spacings are determined by the terrain. The basic structure is an electrified hingejoint/ringlock fence and a secondary offset electrified wire and earth. We used a special steel post called "cliplock ", which have an insulated plastic insert along one side that is designed to work as an insulator and holder for the hingejoint. The hingejoint is strained and just clipped into the holders on the post. While the design idea of these post is excellent we have found the quality to be very poor and the plastic insert breaks easily and does not exactly fit the wire spacings on the hingejoint. We have since been told of another post  "Fibopost XT", (www.sammindustries.com.au) that is a conventional starpost design, made out of a recycled material that doesn't conduct electricity and is very strong. This could be a sturdier, cheaper option. The offset wires were run out using wooden ironbark droppers (drilled to take the tie wires), though a cut down Fibopost would work.The dropper is attached to an earth wire at the top.
The bottom wire is live and 20 cm above the ground and 30 cm out from the hingejoint, the wire above is an earth and about 20 cm above the live. We felt that this setup would work best with the very uneven ground where the lambing paddock is sited. We had the challenge of locating the paddock where there would be plenty of shelter for the lambing ewes as well as being possible to fence.

The gateway has also received special attention, with the gate being swung very low so nothing can go under it, and along the top we placed a spring electric gate wire, to discourage anything climbing over. This same spring gate could be used at the bottom of the gate as well if there was a gap.

We found this fence to be very effective, we didn't lose any lambs from this area, and stillborn lambs were left untouched.(Except by crows) 

We have had some requests for more information about our electric fences for predator control, so here goes. When we first moved to "Riverbourne" there were very few internal fences and we needed to get some in place as quickly and cost effectively as possible. So we decided to go electric, this has worked very well and during the drought required minimal maintenence. However, with the last two wet years the need to keep the grass down under the fences to stop them from shorting has become a bit more challenging and spraying the fences lines with Roundup is time consuming. The fencing has also had the benefit of making our place less attractive to other animals such as wild pigs who tend to go round us to the neighbours rather than come through the fences.
The wire configuration on the fences varies with the paddock's usage, if you just want to keep sheep in, three or four wires will do, but for predator control Gallager, who make electric energisers, recommend an earth wire 2" above the ground, live 4" above that, earth 4" above, live 6"" above, and so on.
We built a lambing paddock like this near the house and for the first few years it worked very well and we didn't lose many lambs to foxes. In the last couple of years we have found that the foxes are coming in more often, maybe they have learnt the fences weak spots, or they learn to move quickly through the fence and only get a shock occasionally. Hunger is a great motivator. The plain wire also makes it easier to get the carcase out of the paddock. So when we needed a lambing paddock on the other block Electric Fence #2 was developed.