The AT&T Merlin - A 1980s Phone System in a Box

[@bigsky1970]

Worked at a radio station back in the late 1980's and we had one of these Merlin systems installed, and as far as I know it's still in use today in 2025. The "breadbox" shared a closet with the teletype machine, as it sat on the shelf near the ceiling, and the printer was on a small table down below. Two published lines, one for the studio, the other for the office, and there was a third unpublished line for remote broadcasts to the studio. So if someone wanted to request a song, the remote broadcast facility wasn't tying up the studio line. Our phones were the usual business black phones. But even after hours if someone called the office line, it would ring all the phones including the studio phone. Very reliable system as I recall. We never had issues with it at least I recall when I was working there.

[@dave1135]

From 1995 to 2003, I worked as a Auto tech at a Goodyear auto service center. We used this phone system, and our service manager had one of these on his desk in the shop. He smoked, and quite heavily, and his fingers had nicotine on them, and ultimately it got on the membrane buttons to the point you couldn't read the buttons. We had memorized what button was what as it was impossible to read them lol

[@chargermopar]

Had a Merlin system I got in 1998. Used it until 2013 when I replaced it with a NEC DSX system due to my mom hating the old Merlin membrane phones. The controller I have includes station cards for analog phones and I had it hooked up to my 1a2 phones. That system still works but is independent now.

[@jeffg9157]

One of these is still in use at a local restaurant. They get tons of phone orders and I here the "daaa doo deee dooo" ring tone.

[@andyreed475]

And 40 years later, Avaya's latest and greatest phones are still using the same ringtones!

[@stereophonicstuff]

It's amazing how timeless they sound. Not at all like other phone systems whose ringers these days sound very dated. The handset design is also quite snazzy if I do say so myself.

[@jfbeam]

One can get those tones for a cellphone. Once you've licensed them, why would you ever give them up. (Nortel also had the same / similar tones. And Avaya bought Nortel's IP in the fire sale decades ago.) I remember the Nortel Meridian phones having those same horrible contact strips. (at least buttons can be easily replaced.)

I never liked that ringing sound. Too simple and harsh. The Nortel phones has a much nicer sound.

[@kennixox262]

I was wondering if Avaya was still around. Too bad that Bell Labs is not.

[@ilyu]

⁠@@kennixox262Avaya is still around (barely) and Bell Labs is now owned by Nokia as their telecom r&d arm after they acquired Alcatel-Lucent in 2016

[@TWA88T]

Brings back memories.

[@quantumleap359]

Our company opted for the Merlin system in 1983. Our company was on lines that must have been in service since the 1940s as there was virtually no electrical spike protection on the POTS lines coming in. Our Merlin used line modules for each incoming line, and periodically, a line would go dead at the voice terminals. I'd unplug the bad module, swap it with a spare we always kept on hand, and send the bad one to a local ATT service depot who would send us a rebuilt one. About 40 bucks as I recall. Overall, I loved the system, and I became the in-house expert on troubleshooting and also the instruction guy to train new employees on voice terminal use. We used the system through 1998.

[@mwjones71]

Thanks for the flashback. When I started in the telephony world many moons ago, I had a few customers that were using the Merlin Plus (the second generation that was a 4x10 by default, but with additional cards could expand to a full 8x20), they were simple, easy to work on, and reliable as all get - in the Information Technology world, we measure things by reliability, there were Merlins, as well as their larger siblings the System 25, System 75 and System 85 that could measure uptime at 99.999% (essentially less than 7 minutes per year downtime). Those systems were all designed by Bell Labs, which also developed the central office equipment used by AT&T as well as the Regional Bell Operating Companies (not to mention military-grade communication equipment used throughout the cold war). They were, for that reason very solid. Now I'm closing in on 30 years in the business, and you don't see the Merlin's hanging around much more. I still deal with the evolution of the large enterprise-class systems, now manufactured by Avaya (after a short time as Lucent Technologies, sadly, Lucent kept Bell Labs - now a part of Alcatel/Lucent, so most of what we see from Avaya doesn't have the robustness that AT&T put into it). One final quick note, if you look at the serial number on any of the pieces of equipment, the first 2 digits should be the year of manufacture, so you can get a good idea as to the device's age.

[@TheOriginalCollectorA1303]

That’s quite the setup! Even though they are ancient by today’s standards, it’s awesome to see that they still work when configured properly! The only unfortunate part is the lack of parts/information like you mentioned, but this video was very informative. It’s cool to see how far a simple analog phone line was evolved to do what this system can. Even more impressive when you think that the Internet was using the same technology. I haven’t messed around with phone equipment like this, but it would be very cool to have a setup like this, and to make it more fun, create an 80s or 90s office with one of those new PC things.

[@stereophonicstuff]

I’ve always had an interest in older telephone equipment so it was only natural to get an old telephone system and put it into service. There was so much information and I have so many accessories and parts for it that there’s enough scraps leftover for a second video. I may end up doing that, but there aren’t too many people interested in old telephony equipment. Glad you enjoyed it.

[@TheOriginalCollectorA1303]

Nice! I wouldn’t know how to even begin on setting up something like this, at least not without a lot of research. I’d certainly try though if I had a whole setup like yours, glad to hear you’ve gotten a lot of use out of it! Someone’s got to keep these old things going, it’s always more fun using these “relics”.

[@johnpanzer2034]

I found a Merlin 410 system in a closed down building on our campus. Was still plugged in and running, albeit with no phones attached. Took it out and brought it home. Plugged it in a few times. Static, lots of static. Replaced all the old capacitors on the power board. That power board was happy for a little while. Then one of the power dividers blew wide open. Found another PSU, put new caps in and it was happy again. Still have some on the logic board itself that need to be replaced. These were common faults on these systems. Right now lines 3&4 are not usable, and if you conference, there is a loud noise that makes it unusable. Either way I’m going to finish restoring it someday. I found a Legend at a great price the other day with CKE4 processor. Hopefully running version 7 (last release before Magix). It will run the entire range of the BIS, MLX, and with the right card, ETR from the Partner system. Very versatile system. With the T1 card I can link it to an IP PBX. Going to do some tinkering soon. Been about 15 years since I’ve worked on a Legend system.

[@stereophonicstuff]

The Merlin 410 that the system in this video replaced suffered a similar fate. It had worked fine for several years, until one day it didn't. DTMF tones sounded like they were being played back on a worn out cassette tape at the wrong speed, which rendered it virtually useless since the ATAs I was using it with wouldn't recognize them when you were dialing a number. My current 410 has a few dead extension ports, but there's still more than enough working ones to go around for my needs. Fortunately, all four CO lines work and are connected to 4 analog telephone adapters; totally overkill, but I have them configured to act as a crude rollover setup, where if Line 1 is in use when another call comes in, it forwards to line 2 and so on.

[@johnpanzer2034]

@@stereophonicstuff yeah I’m reticent to power up my 410 but every so often. I did find a 16 port MLX and 16 port ETR board very cheap so now it can run the whole gamut of Partner, Merlin, and Legend handsets all in the same system. Only downside I found is the PRI in Merlin Legend systems was never fully developed by Avaya/Lucent so you get a number but no name display calling into the Legend system. Still overall a great setup and allows me to preserve my 410 unit’s longevity and do some work to it further down the line. I’m planning in the future to have a small museum/display where I can showcase stuff that I’ve worked on over the years (computers/phones/electronics/etc). A bit of a personal endeavor but something I can take some pride and nostalgia in.

[@electronixTech]

@@stereophonicstuff Regarding the DTMF tones going bad, I wonder if it's the crystal that is used to generate tones is bad or the related capacitors/circuit with a failing component that's causing that.

[@SlappysAutoRepair]

Any update on this? I have a bunch of these systems and would love to find out what other people do on the component level to preserve them.

[@peztang.9459]

I worked on the development of these later on. The phone design concept came from a very well known NYC design firm led by Henry Dreyfuss. Very sleek design with the flat feature buttons, red and green LEDs and a distinctive non-symmetric handset with a lot of emphasis on usability. The phones were made at ATT Shreveport Louisiana works with primary development in Holmdel and later Middletown NJ.

[@DanburyDK]

I did a tech job a few years ago and I complimented the phones the woman used and she told me that her husband worked for the Henry Dreyfuss firm and how he helped design that phone. My jaw hit the floor. I told her about my love and passion for bell system telephones and she was so kind to give me one of the telephones from her home. It means a lot to me as a telephone collector knowing that someone who designed that phone and used that phone in their own home. And now it’s in my collection. She told me how he had passed on a year earlier and I was sad that I couldn’t meet him but she was one of the most special clients I’ve ever worked with. Names will be kept out of this post for privacy.

[@GOPRepubliklan]

God YES. Simple and it WORKED! Beautiful engineering. My former company decided (against my advice as the IT guy that has to maintain it) to replace their 1990 Merlin (perfectly fine with a room full of spare parts) with an NEC system in 2011. Right after, Windows 8 came out. I ended up changing careers. Now I scuba dive and inspect bridge foundations in Michigan. Love it. F Microsoft and F NEC.

[@GOPRepubliklan]

Nothing against NEC, everything worked great (and they are still using it 15 years later when it had a 7 year life expectancy) but it was WAY OVERCOMPLICATED and frankly overwhelming but I get it's Japanese and pretty typical.

[@ogalief]

I hear you there, I used to be an IT guy (on the sysadmin side) and now I’m a commercial pilot

[@owenperkins]

The house I used to live in (big old Victorian) had one of these Merlin "bread boxes" on the wall in the basement, and there was a big box of phones (BIS-10s I presume) up in the attic. Jacks all over the house, including one on the back patio with a cover that looked like a central vacuum wall inlet. It even had a speaker and button at the front door, and a door strike latch release all tied in. Sadly by the time I moved in the system was no longer in use and there wasn't even landline service active in the house anymore. I kind of regret not reconnecting those phones and trying to get it to work again...especially hearing the ringtone they had! Super cool.

[@TheJmich2001]

Most beautiful and unique ring patterns on Earth

[@ManiacalMichael504]

In the early 1990s the school I went to had a Merlin system. Once I was sick and spoke to my mother through this. By the end of the decade they were mostly gone.

[@coreybabcock2025]

9 for a outside line

[@TexDrinkwater]

Wow, this brings back memories. We installed a Merlin Legend system in our manufacturing facility in the late '80s or early '90s, and kept it running for ages. It was installed because the existing 25 pair cable was running out of usable pairs, plus we needed more stations. We finally had to replace it when it got to the point where it was impossible to maintain.

[@azmrblack]

I remember those being so ubiquitous as a kid - I always wanted one for some reason LOL.

[@greendryerlint]

Nostalgic video. I did POS and telecom support for a large restaurant chain in the early 2000s. These were mostly ubiquitous. I stopped doing this work by 2006 but there were still plenty in use at that time. They were basically indestructible. I remember seeing more than one where the cabinet was slightly melted from high ambient heat and the cards in it looked baked but everything still worked fine. I had spare cards and a couple of spare processors, plus spare phones on hand for the rare times there were failures, usually after severe thunderstorms. I think I still have a few of these phones and cards in a box in my storage unit somewhere. That and some parts for the Partner II system and misc. Nortel. My best source for cheap parts were getting these from ebay from closed businesses. Just for grins I just checked ebay and there are still tons of these components around, mostly pretty cheap.

[@batmore1]

Best looking business phones ever! Especially the membrane sets. Very sleek and actually well made. Ours got replaced by the Partner system which had more features but the actual phones were very cheaply made. Thanks for this great video and explanation. I miss the Merlins, glad yours is still in operation.

[@OVCArchion]

Too many memories of these, both good and bad. And lots of time at ext 10.

[@83Roboto]

I worked at a business that had one of these system and I always liked it.

[@orionfl79]

I had a few of those General Purpose Adapters for my old system way back. I mainly used one for an answering machine so I could transfer people to "voice mail", another for the fax machine, and the last was for an old 56k modem. At one point, after fax machines went the way of the dinosaur I wound up hooking up a second 56k modem and just to play around I'd place calls over the system from one modem to the other and connect to an old copy of the Wildcat BBS system I had running off an ancient dos box. :D

[@orionfl79]

Also if I remember right, I think you can customize the ring tone per line by going into program, selecting a line button, then pressing speaker. Although I'm not sure if that was tied to one of the later feature packs.

[@stereophonicstuff]

With my system running Feature Package 2, I can change the ring tones. I remember discovering this after seeing it mentioned in an old KZbin video. Oddly enough, I couldn't find any mention this "feature" in the manual. I've also been thinking of getting one of those General Purpose adapters. Let me know if I'm wrong, but from what I can gather, it seems that they require a Merlin phone as a go-between to connect to, unlike the Basic Telephone & Modem Interface that connects directly to an extension port on the control unit. Also, it seems that the General Purpose Adapter can't actually ring the analog phone that's connected to it. The main Merlin desk phone will ring, but that's it. I've tried to do some more research on this, but by this point, info is quite scarce aside from some old digitized manuals I found online. I

[@orionfl79]

@@stereophonicstuff YES! Actually you're right. I forgot the gpa was tied to a phone (like the speakerphone and headset modules with those weird keyed cat5 type connectors) and the btmi connected straight in as though it were a Merlin phone. Its been ages since I've had that system but I did find an old doc I used as sort of a cheat sheet. Although I'm not sure if its from my old 410 or the later 820D2 I used before it decided to poof into a cloud of magic smoke. System administration mode: From operator's console, program mode → #49 (or hold button). Number of lines (2) *42 → Administer Reference: Central Programming: From operator's console, program mode → #49 (or hold button). Touch the auto intercom button for target. Touch Conference. Program as needed. Touch Conference. Copy programming from one terminal to another: From operator's console, program mode → #49 (or hold button). Touch Auto Intercom button of source. Touch Copy (3rd row, last button). Touch Auto Intercom button of target. Touch Administer. Terminal Programming Reference: Ringing Options (touch line button to select). *35 - No Ring *36 - Delayed Ring *37 - Immediate Ring Auto Answer-Intercom: *70, desired feature button. Auto Intercom: Touch desired button, *91, intercom number. Page All: Touch desired button, *91, 70 Intercom Preference (assigns default line to intercom.): **** Redial: Touch desired button, *73

[@nannesoar]

The fact that they come in 10 different shades of brown is so perfectly 80's

[@themaritimegirl]

Great overview!

[@stereophonicstuff]

Thank you! I recall watching your overview of your Nortar Meridian which inspired me to do this overview of the Merlin. I almost went with a Meridian at the time when I was deciding which system to go with. I still have a whole Meridian system as a backup if the Merlin ever decides to hang it up.

[@ChristinaSmith-e5e]

I use to install them back in the 90. I can remember doing a hack for music on hold, instead of of buying the module (expensive) we used to take a couple pins out of a DB25 female and punch them down on the main board and solder up a 1/8 jack mounted on the blank plate.

[@voiceofjeff]

I remember my first Merlin system. I think I paid $600 for it, used. This was the mid 80s. They were great little systems. Maybe I need to reinvest in another. And I laughed out loud when you mentioned the MP3 player for BG music. Ive been doing the same thing for years! Be well, friend!

[@jeffmoss26]

Had one of these at the hardware store I worked at in 2004. They lasted forever

[@ocsrc]

I have this system in my house. It was a dream of mine to have it. I remember hearing the ring the first time and I loved it.

[@MichaelAStanhope]

I still have my Merlin Classic 410 in storage. Used it at my stepdads garage for about 10 years until we upgraded to an Avaya ipOffice 406 (now 500) that he is still using. I use a Partner ACS in my house. I should dig mine out and give it a clean up. Most of my membrane phones died years ago, I think I still have some 5-button ones left that work, but all of my other ones are HFAI models now that will likely outlast both my Partner and ipOffice systems!

[@TheOtherBill]

I was working at AT&T in Freehold NJ back in '81, my office was a beta site for this system. It was unlike any of the previous phone systems we'd ever seen and took a week to get used to. The hardest part was not calling them phones, they were "voice terminals".

[@5060Presents]

Back then, it was the era of Category 3, which in 802.xx protocol was 10 to 100 Megabit Ethernet, depending on length.

[@joenichols590]

We had a Merlin system at work till 2001 when we switched to the Lucent Partner system we had the Biz 10 system

[@Subgunman]

One upon a time back in the 80’s I had one of these units in my home. I don’t remember why I got rid of it but it was an excellent system. Went to an Avaya Partner system back in the mid 2000’s until lightning fried the processor card. As for that POTs line adapter, check the caps around the power input side of the board. Many times a capacitor will short out or go out of spec and inhibit the adapter from working. Cost permitting you could just replace all of the electrolytic caps, sometimes even those green epoxy dipped will go bad with age.

[@lutello3012]

0:02 Yes, my childhood! How many people had those at home? We had 3 of those and 2 lines.

[@DGNYY27]

We had these at home.

[@vancegosselin]

Oldie but a goodie 👍🙂

[@tgivy]

These really were rock solid systems. I had a Merlin Legend in service that took a direct lightning hit on the line card. It caused the chips on the card to explode. I popped in a new card and the system worked perfectly for another 8 years. Didn’t have to touch any of the other cards or phones. I still have a Merlin Magix in my house. I’ve thought about changing to an IP system but the Magix is way too reliable. The only complaint I have is the clock runs fast.

[@davide60639]

Thanks for the great video! I love seeing older tech still kicking.

[@fdrtech]

Here at the CO unless we get a ticket the warning lights mean nothing 😆

[@عبدالعزيزالواصل-ص6س]

Very Informative! Much respect

[@sartainja]

Remember these systems very well. These phones were designed well and superbly engineered to last. In those days, believe it or not, things were built that way. Realize that it is hard for young people to gasp that concept in their disposable minds nowadays. Thanks for reminding me of my glory days during my youth. Amen. Will get off my old man stump and shut up now.

[@5060Presents]

Used to have the AT&T MOH device, which was a white tape deck that looped voiceover and connected to a mono music source

[@idahofur]

I had a Merlin 206 system a few houses ago.I installed it using cat3 and boxes. The boxes I used was the good old RJ45 that support the 12, and 45 clip? Sorry forget the names. Allowed me to use normal phones if I removed the system. I also had a 410 box. I never did track down a cordless phone for it. But I did have a Merlin ATL box used for a standard phone I used a cordless on. What I didn't realize was the Merlin was a bigger system than a Partner system. Let see if I can remember. 206, 410, 820, Plus, 1030 / 3070 (2 1030 units linked), Legend and magic. The numbers was a great idea. Example 206 was 2 lines 6 phones. Now all I got is several partner systems. Just for collecting. Even though not needed. The partner systems came with 4 pair 8 pin connectors. So you could upgrade your whole system to a partner. Partner though only used 2 pair or 4 wires.

[@stereophonicstuff]

A few years back, I was actually considering getting an older Partner system to toy around with. I've always liked them, and they seem to have totally disappeared from service out in the wild. I also have a rather large Norstar Meridian system as a backup for the Merlin, which as you mentioned, can be easily adapted to use (in my case) the preexisting Cat5 cable. I'd need to get a patch block and a 25 pair amphenol cable to wire things up, something I didn't have to do with the Merlin since it uses RJ45 ethernet style jacks. I'd really like to put the Meridian into service (I like the way intercom calls are handled and behave like outside phone calls with a regular ringback on the Meridian), but the Merlin has been so reliable that there hasn't been a need to do so!

[@idahofur]

@@stereophonicstuff Right now IP office 500v2 systems is going for cheap on ebay. Took me a while to track down a used working partner edition with 2 etr cars in it. However, That system only supports the euro style partner phones. Not the old ones. the system also does meridian/nortel, standard digital avaya digital phones and voip. Though due to licenses. You can have 2? sip trucks into the system. But no more than that or any voip phones until you purchase additional endpoint licenses. Compared to other hybrid digital / voip systems. I think that was one down fall. You can't even purchase a Avaya phone and have it work with out a license. You would think it would be included with the phone.

[@johnpanzer2034]

@stereophonicstuff There’s a reason Partner systems are largely gone. They had a very high failure rate. The ports would sporadically go bad. Sometimes whole boards would go bad also. The heat those systems generated was trapped in by the design of the chassis as the plastic parts would absorb the heat. Often you’d take boards out and they’d have what looked like burn marks on them. That is where the system would overheat and discolor the plastics. Very bad design.

[@rkolsen]

Do you have any information on an AT&T teleconferencing system where you dialed into direct lines for a meeting? Maybe back in the 1980s. In 2004-2008 I did distance learning over the phone for HS and each student could dial in / out dial out. The teachers console was just a long box where you could be moved to private, and separate rooms.

[@videosuperhighway7655]

I worked on that and Definity G3 systems as well.

[@jaytitus902]

Look how perfect that documentation is. Must be because the service center number was PLASTERED all over the place. Internally and affectionately referred to as Merlin hotline HELL.

[@andyreed475]

...and all those numbers still work!

[@alberta.shammah7360]

Had this at home from 1986-2004 replaced, by a Notel Cics, replaced by a Nortel BCM, replaced by Freepbx 2025

[@rustynail6819]

Ringer brought me back to 1985.

[@LAURAMORENO-y8s]

Trying to change from pulse to tone ... please advise, Thanks!

[@stereophonicstuff]

If yours is like mine, there’s a switch right on the control unit. Just switch it from pulse to tone.

[@kennixox262]

We had those in the USAF back in the 1980's and the most annoying phone ring. I knew a guy in t he 1990's with a "phone fetish" who put a Merlin system in his house.

[@The.Orchard]

I appreciate this historical presentation but you need to do a bit more research. BIS literally stands for Built-In Speakerphone. There is a microphone inside any BIS model. If you see a button labeled HFAI, that stands for hands-free answer incoming which is for intercom voice calls. The system you're referring to that had voice versus ring intercom buttons would be the Merlin II, which essentially became the Merlin Legend. That one had a crazy attendant console that had its own gigantic external power brick but otherwise looked very much like a Merlin phone just the width of about three of the 34 key stations in one. The next step up from that was the System 25, which was essentially a modern for its time hybrid switch that could have two cabinets and could use any of these phones as stations. The legend also could, but even display models like the BIS-22D qnd BIS-34D didn't have addressable displays for modern functionality like caller ID although they could show the calling extension. But even on system 25, they would have to have their clock set locally because despite the switch knowing the time and date it couldn't send it to the phone and keep it updated. Essentially that was their only function was to show the callers ID for internal calls, the number dialed, a call timer, and locally set time and date.

[@akshonclip]

Back when you were forced to lease your equipment from the phone company.

[@2dfx]

Interesting kit for sure. I can see why Nortel basically dominated this space.

[@xusmico187]

great phone until power went ot....