Rca?

[zorlac]

For starters, count the buttons on the front. The DRD22x models have three - power, channel up, and channel down. The DRD420/440/480 receivers have seven - power, menu/OK, Up, Down, Left, Right, and Info.

Also, check the connections on the back. DRD420 receivers have one set of RCA audio jacks and one RCA video jack. DRD440 receivers have two sets, along with a VCR blaster output. DRD480 will have all of that plus an optical output and RF remote connection.

I think the service menu may also tell you the model number, but I don't remember. With the receiver on, try holding LEFT + INFO on the front panel for about 5 seconds. It may be RIGHT + INFO, but I thought that was for resetting.

[zorlac]

If you had a DRD221/222/223, rest assured it only had THREE buttons. They didn't add the extra buttons until the DRD420/440/480 series came out.