Electronic Pet Doors
Electronic pet doors or automatic dog doors have become more reliable over the last few decades. While the smaller, inexpensive electronic doors function well, these electronic cat flaps aren't as weather tight as a good quality non-electronic door. The best reason to get an electronic dog or cat door is to keep a stray cat from getting in and spraying to mark its territory (YUCK!) or to keep rodents and raccoons out.
One thing most electronic pet doors DO NOT do well is to let one animal out while keeping another in. If you only have cats and one or more isn't allowed out, the SureFlap DualScan (and only the DualScan, not the other SureFlap variants) will do that job.
Many people have a dog and a cat, the dog is allowed out and the cat isn't, and they think that an electronic door will solve their problem. There are a couple issues with this. Most of the smaller doors lock one way only, so anything inside the house can get out, but only pets with the keys can get back in. The other problem is that the doors have to close to lock, so if the cat and the dog are buddies, the cat can go right through the door following the dog. They do not slam shut for obvious safety reasons. The High Tech and Electronic Plexidor are like miniature automatic garage doors for your pets, where the rigid flap opens and shuts vertically. They close very slowly and are not powered down, and instead close by gravity. This leaves lots of time for a cat to run through the opening after the dog has gone through.
We don't carry radio fences, which are shock collar devices, but there are indoor versions of these that can be used to keep a cat in. Understandably, many cat owners don't want to shock their cats, but at least it is a solution that works, where an electronic pet door won't.