I have an older TH series Speco Technology DVR and I'm looking for inexpensive low light IP cameras that will work with it. The largest frame 720 H.264 stream. All of these newer cameras seem to have encryption.
From some digging online I think I have found the specs for a model that is part of the TH series and I cannot see any mention of ONVIF support (probably because of its age it pre-dates ONVIF), this means your recorder will likely only support Speco cameras and so you will probably need to look for a 2MP Speco camera. (nobody produces 720p cameras anymore, but with a 2MP/1080p model you should be able to set it up on your network, reduce the stream to 720p/H.264, and then add it to the recorder)