I was doing a bit of research to see if DTV was controllable via RS232 and it seems to be possible using different methods depending on the model you have. Although my HR23-700 DVR isn’t listed anywhere as confirmed compatible by DTV and doesn’t have RS232, it does have USB.
There isn’t much i could find on the internet that suggested that this model will work but i was experimenting with a USB/Serial adapter and managed to get it to respond to commands from a PDF doc I found for older receivers.
I tried to search here but any idea if anyone ever wrote a plug-in for this as i cant find anything?!