EEVblog 1587 - Dumpster FAX Teardown

[EEVblog]

Teardown of a Brother FAX machine found in the dumpster, just because.

[nctnico]

I used to have the smaller brother of that machine. I recall It always worked like a charm but don't ask me where it ended up though. It is long gone. Can't remember the last time I send a fax.

[coppice]

FAX is still a substantial business in some large niches. I know people who still make their living entirely from FAX services, and I have a request right now to sort out a problem in a large FAX service, because their upstream service has made some voipy type equipment changes they need to tolerate.

[nonlinearschool]

Pharmacy's, doctors and lawyers.  Digital signatures not accepted

[Kleinstein]

I have still use a fax machine this morning, though only as a scanner.  I still have it, the few rare fax receptions are handled by the phone router. At least in Germany the transition to VOIP for the phone system essential killed FAX. Many machines can not handle the bit of extra delay and failing transmissions are common. Looks like the delay is just in the wrong window so they don't switch to a more tolerant protocol for international (long cable or even satelite).

[nctnico]

I have still use a fax machine this morning, though only as a scanner.  I still have it, the few rare fax receptions are handled by the phone router. At least in Germany the transition to VOIP for the phone system essential killed FAX. Many machines can not handle the bit of extra delay and failing transmissions are common. Looks like the delay is just in the wrong window so they don't switch to a more tolerant protocol for international (long cable or even satelite).

Delay shouldn't be an issue. More likely the problem is how the audio is compressed and the stream is synchronised when using Voip. Back in the old days, the digital telephone system was entirely synchronous so digitized audio would be played back at the same rate as it was recorded. With Voip, that requirement is no longer there. Samples get repeated or dropped to synchronise the audio at the receiving side. When a packet is dropped (buffer underrun), the last packet that was r eceived simply gets repeated. This isn't a problem for speech but for a modulated signal, it is killing. Compression poses a similar problem. It is optimised for speech but on a link with a limited bandwidth, the bitrate may drop. Again this is not much of a problem for speech.

[coppice]

I have still use a fax machine this morning, though only as a scanner.  I still have it, the few rare fax receptions are handled by the phone router. At least in Germany the transition to VOIP for the phone system essential killed FAX. Many machines can not handle the bit of extra delay and failing transmissions are common. Looks like the delay is just in the wrong window so they don't switch to a more tolerant protocol for international (long cable or even satelite).

Delay shouldn't be an issue. More likely the problem is how the audio is compressed and the stream is synchronised when using Voip. Back in the old days, the digital telephone system was entirely synchronous so digitized audio would be played back at the same rate as it was recorded. With Voip, that requirement is no longer there. Samples get repeated or dropped to synchronise the audio at the receiving side. When a packet is dropped (buffer underrun), the last packet that was r eceived simply gets repeated. This isn't a problem for speech but for a modulated signal, it is killing. Compression poses a similar problem. It is optimised for speech but on a link with a limited bandwidth, the bitrate may drop. Again this is not much of a problem for speech.

Yep. Compression and synchronisation are the issues. Delay is an issue for other modems, but FAX works in a ping-pong manner, and unless the delay becomes super extreme it doesn't matter. Carriers send VoIP FAX calls around successfully, because they groom the calls to use only A-law and u-law compression AND they have switches with atomic clocks. As long as their packet loss rate is close to zero FAX works just fine. Other modems may also work OK, although they are more sensitive to delays. A lot of people can groom the codecs, but getting the timing right is more of a problem. FAX over VoIP really needs T.38 if you are not a carrier with tight synchronisation.

[ballsystemlord]

@Dave , I've never seen you tear down something that I have torn down before. Your model is missing the phone. Yes, really.

As for if there are any niche application of faxes, the answer is that they're still used in businesses here in Florida USA. But what you really really do-or-die need them for is if you want to send anything to a government office. The gov. places here have email. They have offices you can drop stuff off at. But they block pretty much all incoming email and they won't allow you, a lot of the time, to physically drop something off. That policy predates COVID19.

I have just one question, you said there was nothing useful in the fuser, but wouldn't the fuser tube be useful to you as an IR heating element?

And to the community, if anyone knows how to get that green grease off, I'd be appreciative. Normally, you'd be able to use dish detergent. But not with that stuff.

Thanks!

[nali]

I have just one question, you said there was nothing useful in the fuser, but wouldn't the fuser tube be useful to you as an IR heating element?

They do indeed... my DIY reflow oven uses a pair of lamps from a couple of scrap fuser units which happened to fit the sandwich toaster I bought for the purpose and has worked well with occasional use since I built it in 2007. Just the halogen strip lamps; the fusing rollers themselves are coated in silicone rubber.