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Henryk Richter

Fritzbox 7360 Rack-Mount

Fritzbox in a Cisco 2501 Enclosure

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What started off as the idea of a basic rackmount conversion of an AVM Fritz!Box 7360 ended up as some quite larger project. Initialliy, I just no longer wanted to have the Box lying around the bottom of my 19" cube. It didn't look nice and it developed cooling issues. Additionally, there was of course the problem of the internal antennas. Obviously, WiFi out of a steel box is never the best of choices.

Hence, two things were most important to me in the beginning: external antenna capability and 19" enclosure. I did not find what I was looking for on the net. Most offerings were using internal cabling from the FritzBox mounted in the interior to the respective front panel. Furtunately, with the rise of 3D printing, I could design a customized front panel for my FritzBox, exposing all ports to the front of the new enclosure.

The second part of the project includes a basic call manager that displays incoming and missed calls on an LCD. We had such a device as stand-alone unit for years now and as it stands, my better half rather looks onto that ancient unit for missed calls than the respective apps on her smartphone. So I went on integrating this functionality into the FritzBox enclosure as well.

The choice for the enclosure was straightforward for me. I had a Cisco 2501 with a failed mainboard at my disposal. The old Cisco two-part enclosure is not optimal for maintenance as disassembly of the two halves requires prying with a screwdriver. In addition, both parts carry electronics. Nevertheless, I have some confidence that frequent disassembly is not necessary.

The project is still a WIP. More information will be posted later.

First try to fit the LCD and Fritzbox into the Cisco 2501 enclosure

Power supply

Important Warning: The steps outlined below are meant to be carried out by skilled personnel only. Working with parts where voltages way beyond 100V is potentially hazardous to anyone's health, including but not limited to risk of fire, etc. The author of this article is an experienced electrical engineer.

In principle, the power supply of the old Cisco 2501 could be perfectly suited for this project. It readily outputs 5V, 12V and even -12V. The PSU looked exceptionally good and left the impression to be able working for years. The catch? It's idle power draw of 4W was not what I would like to run 24/7 these days. Regardless, the outputs of that original power supply are quite suitable to power a FritzBox (12V) and an additional USB Hub (typ. 5V). I advise to keep the original PSU in case that anyone is going to start a remodeling project similar to mine.

I chose to replace the PSU electronics by the contents of two low power plug-type PSUs, one with 12V and another with 5V, respectively. The secondary voltage areas of both PSUs were soldered to a Veroboard and secured with a combination of hot glue and plastic spacer material from an old PC PSU.

Bottom Line: same form factor of the PSU keeping the original socked and external on/off switch -- but just a fraction of the idle power draw (about 500 mW). A bonus for the two PSUs is that they now get a considerably better airflow.

Placement of boards in the original PSU enclosure
Insulate Boards by plastic spacers from a PC PSU
Insulated top of PSU enclosure

Front Panel Design

One of the biggest hurdles in such a mod is a decent front panel. Precisely dremeling and filing 1mm hardened steel is not what one does happily in his spare time. So I came up with a different approach. Thankfully, 3D printing has gone mainstream these days. I grabbed myself a copy of Sketchup Make and started designing my first model for 3D printing.

The frame for the front panel is 2mm thick around the ports and 1mm on the edges. This way, I could fit the panel into a hole dremeled into the front of the enclosure, while leaving some headroom for eventual inaccuracies. The panel features two extensions on the backside. These hold the mainboard of the FritzBox in place, secured by two push-pins from an old graphics card.  The panel features two additional mounting holes for external antennas (RP-SMA).

After finishing the design of the FritzBox front panel, I thought a little more about the features of the final box. What came to mind was a CallID display, directly as part of the box. The LPH8731 display is small enough for a 1U enclosure and went into the project. It's mounting frame was designed using the same principles as  the FritzBox front panel. I placed four snap-in locks on the backside.

Backside of the front panel
Frontside of the front panel
Display mounting frame front
Display mounting frame backside

3D printed parts

The photos below show the result of the first attempt to fit the 3D printed parts with the electronics. I was quite impressed with the accuracy of the prints.

The light from the status LEDs is passed to the front via fiber optics (2mm POF). I glued the fibers to a detachable mounting frame on the back of the board. This way, the FritzBox PCB can be swapped out at any time. In fact, I used a FritzBox with broken DSL as template for the prototyping phase.

Front panel with FritzBox PCB
Fiber optics
Display with callID and rotary switch
Display mounting frame

Enclosure, bottom half

Bottom half of the Cisco 2501 enclosure

The bottom half of the enclosure is housing the PSU, the original fan (supplied by 5V for less noise) and a USB hub. I've also put two USB ports to the back, along with an old-style 10 pin Atmel programmer port. The internal cabling is secured by velcro strips.

What can also be seen in the image is that I just couldn't get myself to overpaint the former model number and manufacturer logo.


Preliminary assembly and initial WiFi test

The picture above shows the first complete assembly. The mounting frames are glued to the Cisco enclosure with epoxy. The Atmega board is sitting directly behind the display. The rotary switch is used to scroll the incoming and missed call list up and down.

My CallID consists of two parts. A script on the FritzBox parses the call list and sends the details (call type, Unix epoch, Name/Number) via UART to the Atmel. The latter refreshes the screen if necessary. In my experience, FTDI chips don't work very well as USB2UART converters when it comes to FritzBoxes. For me, it started with sudden crashes, followed by sporadic reboots with other drivers (original AVM supplied driver, various other drivers via Freetz). I could improve the runtime behavior by disabling the echo channel. In the end, a better working solution was to replace the FTDI by a PL2303HX board. The PL2303 driver is also available via Freetz and ran without a hitch in my case. Problem solved.

The cables for the antennas were not so easy to find. The 7360 doesn't have the usual U.fl sockets but rather just two Hirose MS-156 test points. The original Hirose adapters are out of the question (~100 EUR each). There is a german company selling external antenna kits for the FritzBox 7360, but their kits include parts I didn't need. In the end, I ordered two MS-156 to RP-SMA cables overseas.



STL file for Fritzbox 7360 front/mounting frame

414 K


STL file for LPH8731 frame

70 K