PBX Phones - Without a PBX?

These phones promise PBX-style features: intercom, paging, conferencing - without a PBX. How is that possible? A clever way to improve very old technology by applying even older technology!

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[ethernet]

the cat notepad sliding into frame every time with the 70’s western electric desk phone progressively becoming what i could only see as car batteries with handsets was great

[Reisperbachtal]

I like how the first phone was drawn really detailed and a bit artistic, the second one was drawn ok and the consequent phones where just car batteries with a whip

[Bear-cmvl]

I am an "OG" phone phreaker, who had access to equipment in the 60's, 70's and 80's to play with (brother in law worked for Bell Systems, and later, Bell South), built POTS intercoms, mini PBXs and even a couple tiny patchboard controlled "hotel" networks.

There were three generations of the "overlay intercom" system designed to work with POTS "plain old telephone systems" and one was actually rented to small businesses by telephone companies like Bell Systems.

Note that I said "rented", not sold, as the telephone companies rented and powered all their equipment from the system before the Federal Government stepped in and broke up Ma Bell into all the Baby Bells. The first gen "simulated PBX" used the 3v DC talk circuit power with a voltage clipper to protect every thing from the 90v AC bell ringing power and used up to three carrier frequencies, allowing up to three parallel intercom functions at once.

The second (which I suspect your white INT phone is) only had one intercom channel (some locked out other stations from intercom and others created a party line, only ringing at the dialed station). Because of the issues with power consumption and frequency reflection on unshielded POTS copper wiring, they had lots of issues with weird and unexpected communications issues and acted like a very leaky transmitter, to the point that you could listen in on them with a decent radio receiver. The Baby Bells refused to power them, both due to the power consumption and because it was a cost they could no longer charge for, so 2nd gen didn't last long (ever wonder why telephones came out with "ringer equivalent" markings and "T/P switches"; Ma Bell was pissed about having to upgrade power supplies and add DTMF decoders, so they pushed back on the Feds!).

3rd gen was more similar to the black pair you tested, were almost always powered by "wall wart" power supplies and could have multiple higher frequency carriers for parallel intercom conversations, could have Frequency Modulated signaling and intercom channels (no static and little interference between the phone lines, DSL data and the data/talk on the intercom lines. The problem was the expense and some special wiring requirements for the higher end systems, requiring small and medium businesses to retrofit their aging phone wires inside the building, even requiring removal of old, mechanical PBX modules, making the retrofit cost ridiculous, but for their day, 3rd gen could do tricks that would make a show pony jealous! Too bad, this was right before the digital revolution ate it's lunch.

All three were very cool, considering how simple the electronics were and the functionality.

[spooforbrains]

All the way through the video I was thinking "oh, dude, this really needs an oscilloscope" and then wondering whether I could use my cheapo mini-oscilloscope to explore similar stuff I had round the house. Then you pulled out the oscilloscope and I practically cheered. I loved this video, thank you. Another person brought here by Alec from Tech Connectifadoodledoo

[TeamSupertek]

I laughed out loud when the cat notepad slid into frame hahah

[anzer]

Thank you tech connections for introducing me to this wonderful channel

[tibipics]

This is some whipass staging with those monitors dude, nice vid

[techsture]

Having worked on Nortel systems for a decade in a previous life, I was more excited than I should have been to see you pull out that old NorStar/Meridian Key System. Great video!

[TheJaguar]

Pretty clever. I feel like a lot of pre-2000 stuff was a lot more innovative because there were more limitations.

[meatsock]

the rackmount multicam is a great way to make a video look like more than just talkin at a camera

[KNFPRadioelectronics]

Good video! I just wanted to clarify some things for people who may watch this video.

The Nortel Meridian PBX, and most other PBXs (not all) use a concept called Digital telephones. Digital phones aren't analog and they aren't IP.
They use a specific system of multiplexed digital signals and digitized audio. It uses a standard called ISDN, although almost every PBX uses different communication protocols, they all seem to use the same ISDN standard. Plugging an analog phone into a Meridian PBX, you will just hear a high pitched whine and that's it. Those PBXs do have analog stations, but when someone refers to a Nortel PBX (or almost any other PBX), they usually use a digital telephone.

One more thing, which you briefly pointed out is what a KSU (Key System Unit) is.

A KSU is not a PBX, a PBX allows you to transfer calls, do paging, and have system applications (like extensions that don't go to a physical device).

A KSU is a device that allows multiple telephones to share multiple phone lines. It also does intra-office calling, and on-hold, but it isn't a PBX.

Again, great video, but for the more technical viewers, I just felt like I needed to point this out!

[djdjukic]

I really enjoyed this video. You cover some rarely talked about, yet well known technology. And you have perfected the mix of "show" and "tell". I know how AM radio works but you didn't bore me with the explanation (and yeah, that's what the phones are using). I love how you brought out the oscilloscope, there's really something about witnessing the actual waveforms that makes signals "click". I know this is a year old video, but I hope you keep making more like this.

[joshuawilliams]

I never comment on videos but I'm going to bite the bullet and do it. Amazing video(s)! I love how you cover all these old technologies. What people take for granted now, cell phones, don't understand that these older technologies really paved the way for our technological advancements that we see today. Growing up as a kid, phones, TVs, and camcorders, where all like black magic to me. Seeing how you explain things, causes the light bulb to go on. Keep it up!

[henrythompson]

OMG, everything I ever learned in 30 yrs of telecommunications! Excellent presentation!

[photo]

Love Gibbs. He deserves his own channel

[Fnordcom]

These things were rather uncommon in European countries. ISDN was heavily subsidized by the phone companies in the mid 90s. Businesses had usually a cheap or free 2 line, 8 telephone ISDN PBX in the back office. Since digital ISDN phones were expensive, mostly cheap analog phones were used. Most of the ISDN PBXes had a certain number of D/A-converters for legacy phones and fax machines. However, the concept of having a cheap analog intercom system with multiple carrier frequencies operating on a single pair of wires is amazing.

[maurice_walker]

Really interesting to see how laws & regulations influence technology. Here in Germany, directly connecting more than one phone to an (analogue) phone line has always been illegal. Of course there was demand for multiple phones in businesses and larger homes, so a thriving market for small, affordable PBXs developed pretty early. Around 1990, my parents got a PBX for 4 phones and 1 outside phone line. A few years later, we upgraded to a larger one which connected a bunch of phones, a fax machine and a door intercom to an ISDN line. This was nothing fancy at all, many families and most small businesses had this.

[NiemandKatzchen]

Still loving these videos! Really good presentation, explanation, and pacing. Also, big props for trying out different style stuff like this CRT array setup.

[Bubu]

"Master phoneset" is when you have a "master phone" and a bunch of "slave phones" that connect to the master phone to ask for an outside line. The phones have to be matched with each other. This was common with cordless phones for a long time. All of the extra phones simply relayed back to the main master phone, and their bases were 'dumb' providing basically only charging.

[anrew]

Best channel on YouTube. I found you a couple weeks back and I’ve been binge watching your content any chance I have. The way you slid that notepad onto the screen reenforced my approval of this channel 😂 thanks man!