This is the D65 Asterisk/SIP phone made by Digium, which is the same group that maintains Asterisk. I would expect it to work out of the box, and it did.... with some work.Okay, first, and most importantly: This is NOT a normal, plug-in-to-the-wall phone. It will NOT work with normal analog phone lines or home-office-style phone service. There is no cord or jack to plug in to your wall phone jack, don't even try! This phone is designed primarily to be an Asterisk SIP endpoint. It can connect to one or more (6, actually!) SIP service providers. If you don't know what Asterisk is, and you don't know what SIP service is, you should NOT buy this phone.To use this phone as it is intended, you must have your own Asterisk- or SIP-based phone system. I am using my D65 with two different Asterisk 18.6 systems, clean installs, with minimal configuration. One is on my local behind-NAT network, and the other is on the Internet elsewhere. My D65 is connected to both, and can make and receive calls reliably from both systems.This phone is generally intended to be used in an office setting. It expects to be plugged into an Ethernet connection, and receive POE Power-Over-Ethernet. The phone comes with the body, a stand, a handset and handset cord, and an Ethernet cable but it does NOT come with a separate power supply. If you're using this phone at home or don't have POE or don't intend to plug in to Ethernet, you'll want to purchase the separate power supply for a few dollars more - it's well worth it. This phone does *not* have Wifi built in, or any other network access, and it does *not* support IPV6.The first thing you should do when you purchase this phone is to power it on and upgrade the firmware. My phone arrived with firmware that was many versions back, and a number of features currently offered were missing. So just make the determination that you're going to upgrade the firmware. This is the only part of the phone that I was particularly unhappy with: My initial attempts to upgrade the firmware failed. This might have been because my firmware version was so very old; but, still, one expects the process to be seamless, and it wasn't. I tried downloading from the website, and unpacking, but the phone wouldn't recognize the file. I tried generating a config file, which also failed. I then tried hand-keying the URL into the phone itself using T9-style typing - and that *also* failed on the first attempt. On the second attempt using that method, the phone finally downloaded and accepted the upgrade, and I'm now on the latest firmware version, which, as of September 2021, is 2_9_13. (I think my phone came with version 2_4_1, which is *30* versions and *4* years back.Once you get on the latest firmware, though, using the phone is a piece of cake. I'm using the Asterisk PJSIP module, and your Asterisk endpoint config in pjsip.conf really only needs something like:allow=!all,alaw,ulaw,g722rtp_symmetric=yesforce_rport=yesrewrite_contact=yesdirect_media=noto connect in and out flawlessly.As you would expect from a SIP phone, it will NOT work well behind a double-NAT, so I had to flatten my home network a bit to get it to single-NAT to connect. In addition, to connect to my remote Asterisk, I had to set the D65 to use TCP on that connection (instead of UDP). But that was just a few minutes of trial and error.Apart from the firmware upgrade difficulty, this phone has only two other negatives, but they are a problem. First: The configuration webserver on this phone cannot be (conveniently) turned off from the server itself or from the phone settings. I'm given to understand you can construct a complicated XML file to force the issue, but that's more work than I feel should be necessary to implement such a feature.Second, and related: The admin password can only contain digits, and only TEN digits at most. Yes, that's ten billion password possibilities, but it just... feels... insecure.One other thing I don't like: The phone gathers fingerprints. Everywhere. Cleaning it is not as easy as it should be. The phone itself is beautiful - nice, crisp screen, but both the matte and gloss plastic finishes just cling to fingerprints, which quickly mars the beauty of the device.Everything else about the phone is fabulous. It's got great sound quality, a great display, a good feel in the hand, easy, comfy buttons, and it *Feels* like a reliable device. I imagine it would work well and reliably with a variety of SIP systems and providers; for me, this is the phone of choice for my Asterisk systems, and as we all prepare for a return to work, I'll be upgrading my office's phones with this unit going forward.