How Does a 66 Block Work? | 66 Block and Telephony Basics for Beginners | Make Money Freelance Tech

In this video, I show you the basics of how a 66 Block works. This video is a perfect way for beginners to understand Telephony.

Performing Telephony service calls on POTS lines is something I do every day as a Freelance Information Technology Technician. I have been an independent tech for over 20 years and this is one way I work efficiently out in the field so I maximize my billable hours.

Link to the Tools in this video:

Want to know where I get my clients, service calls, or want me to cover something I missed in a video? Feel free to leave me comments and I’ll do my best to help! You can also communicate directly with me through my website or sign up for one on one coaching:

Subscribe to Field Tech Academy’s YouTube Channel:

I have been in the freelance IT tech industry since 2000, on Field Nation since 2010, and on Work Market since 2011. Field Tech Academy wants to give you the secrets of 20+ years of experience how you can succeed as an Independent IT Field Tech.


Connect with us!

Contact Us:


Support The Channel!

Love the channel and want to support our work?
You can go to the “Tip Jar” on our website to leave a tip:

You can also support the channel by clicking this link to Amazon before you make a purchase. For the next 24 hours, we get a small commission for the things you buy:

Video Transcript:

If you ever looked at a 66 block and you feel like it is a piece of alien technology, then this video is for you.

If you’re doing I.T. field work,

there are a lot of calls that are offered that deal with


66 blocks,

and old school POTS dial tone lines.

Hopefully this information will help you feel more confident about taking some calls that are related to telephony. Let’s get into it.

In today’s video, we’re going to talk about the basics of 66 blocks.

A 66 block

is for telephone systems

and for “POTS” lines.

Some 66 blocks will be pre terminated to a 25 pair.

These little gray cables are called amphenol cables. And they actually can carry all 25 pairs off the 66 block to another device.

The nice thing about Amphenol cables is one cable connects to the side of the block and has all 25 pairs pre terminated.

Makes it very simple to bring it to another device.

On the back, all 25 pairs are pre terminated and are connected to each of the 25 pairs here. So your total of 50 rows and 25 pairs.

A standard 66 block does not have anything pre-terminated to it.

A block that is

stand alone or one that has amphenol connections will have a bracket just like this

that will attach to the wall you just put in your screws and you’ll be able to just snap in your 66 block.

Let’s talk about the principles of the 66 block.

Each one of these connectors,

as you can see, if I move this connector, this one moves with it. See how those move in unison? These two are connected in the back. It’s basically a U-shaped connection that you’re seeing the top of the U on.

If you connect something to this pin, the same signal will be live on this pin, but it will not be automatically on this side of the block.

So you’ve got the right side of the block that has two pins over here. The left hand side of the block, which has two pins over here. So anything you connect to pin one will be on pin two. Anything you connect on pin three will be on pin four.

Most of the time

what you’re going to see, is that a telephone company is going to bring in their cabling on one side or the other of the block.

There’s no set standard to that. So it can be brought in on the right side of the block or it can be brought in on the left hand side of the block. So if you’re wanting to take a phone connection from the telco and take it out to your equipment,

you’re going to need to punch down your wires in such a way that you’ll get the signal from the telco over to your internal equipment and your internal wiring.

Most telephone guys will carry around a spool of cross connect wire.

This is just a two conductor, one pair cable. Typically blue/white and white/blue.

When you’re dealing with

most simple phones,

old school POTS phone systems,

all you need is a tip and a ring.

There’s a lot of digital phone systems that also will use just one pair.

To punch down a wire into a 66 block, there’s a little gap, a little opening right here as you can see my screwdriver going through it. You want to force your wire down into those teeth and that will actually grab

the conductor,

split the jacket, and make copper connect to the pins.

A standard POTS line just needs one pair.

Tip and ring,

and it’s not assigned a particular color.

For example, if you were going to terminate a cable onto this top pair, we’re just going to bring the wire over, kind of do a 90 degree turn right there, and have it partially gripped into those teeth.

You can terminate this with a screwdriver in a pinch, but that is a pain in the butt and it’s not going to make a clean connection. You want to have a punch down tool and you want to have one that has a 66 block blade. As you can see on this side, it is flat. And on this side it’s a little higher and it’s sharpened here.

This is the cut side as you see on your tool. It’s going to say cut.

We want to cut this in such a way that we leave the conductor inside those pins so we do not want to cut it from this angle. But the cut side on this side, we want to cut the tail off. So I come around the side.

And this opening right here will actually fit over this pin and wiggle it down on top of it. And then you’re going to pop it to actually cut off this tail.

And you can see the tail is now loose and off.

the reason you want to cut this off cleanly is because you can’t have this pin touch this pin or it will short out your connection. Now that we’ve done the first one, we’re going to bring the second one down to the opening here. And again, we’re going to loop it over the connector and get it down into those teeth just partially like that and hold it in place. Again,

we’re going to go cut side down

and then we have our tail off. And as you can see, we’ve got a good, solid connection.

For illustration purposes, I’m going to use a tone generator to show you what it’s like to send a tone down the line just like if you had dial tone going down the line.

On Buttsets, and on tone and trace sets, you’re going to have alligator clips.

As you can see, there are angles to these that would allow you to put them on the block and have them pointing away from each other so they’re not making contact to short out the signal.

The other thing that you’ll see on the alligator clips, is you’ll have a “Bed of Nails”. Basically, it’s a bunch of pins sticking up

and you can use this to pierce the jacket so you don’t have to actually strip your wire back to raw.

You can just lay it on the bed of nails, punch it down. And by punching down, I just mean squeeze hard. So that should pierce the jacket and send our signal down the line.

I’m going to use my tone generator. I’m going to listen to see. As you can see, when I touch it, I get a really good loud signal.

I’m still going to get some halo sound. So no way to really know if you’re on the right pair. See how it stays quiet. But when I get on the right pair, it gets really loud. So I know that I’m getting my signal down the line.

Let’s pretend that this is the telco side. I want to bring another wire out on the right hand side to go out to my equipment.

That’s where bridge clips come in. Bridge clips carry the signal across from one set of pins to the other set, thus bridging it.

Without the bridge clips, you can see that we have a strong signal here. We have nothing but a halo signal here.

This one and this one are the same.

There’s no strong signal on this side.

So let’s say I was bringing in my equipment to this side and I put this one on the second set. Again, my cut side needs to be on the

down side.

Bring in my top one to the top conductor.

I’m going to make sure my tails are out.

So now I have, in theory, the telco wiring come into one side and my equipment wiring going out to the building to where my equipment is.

So I have good strong signal on this side. But if I go to this side, I don’t have a strong signal. I’m still just getting the halo signal.

Nothing strong here, really strong on those two.

Now I want to actually convert this signal from the left side to the right side of the block. So I’m going to use my bridge clips.

And slide one here. Now, I should have good, strong signal and I’m going to actually move this away. So I will have good signal here on this side. And if I come to this side, I will have strong signal because I’ve carried the signal from the left side to the right side.

I could have brought my equipment wiring to this set of pins and not had to use the bridge clips. The reason you want to use the bridge clips are so if for some reason you have problems with the internal wiring, you can remove the bridge clips to be able to do testing. Because if you’ve got a short on your building side and it’s killing your dial tone, then pulling off the bridge clips will allow you to test on this side to see if you have dial tone.

If you have dial tone on this side and then suddenly you put your bridge clips on and the dial tone dies, then you know, you’ve got a short somewhere on your internal wiring. So you need to trace this out to find out where the short is


tool that you’ll use in telephony to do troubleshooting is a Buttset.

A Buttset has several options. You’re going to have tone and pulse for the signal type, and this is how it dials.

Pulse type is the old school rotary circular dial on it that you’ll

you know, you dial it away from the nine up to the stop point, let it go, dial the two, it’s shorter, etc..

So if you put this on pulse, when you press these buttons, it’s actually going to send a pulse signal and not a tone signal. 99% of the time you’re going to be using tone.

This button is a last number redial button. This allows you to just hit this and it will redial whatever the last number was.

You obviously have to have it connected to an active dial tone powered system for this to work.

Right now, I’m not plugged into anything. This button will not work.

This button is your handset functions. Just like a desk phone or an old school POTS phone, there is off-hook where you pick up the receiver, and on-hook or you put the receiver down. But this also has a monitor feature. A monitor feature allows you to listen in on the line.

This is beneficial so you can actually get on the line, go on to monitor and listen for static, listen for noise, listen for distortions. You could theoretically connect to an active line where someone’s in conversation or you can make a test call and listen to hear any distortions. When you’re on monitor and you speak, they won’t hear you speaking.

All you’ll be able to do is you’ll hear them. They won’t hear you

This is a fluke on this particular one. The middle setting is on-hook, which basically means that the call is hung up once you move it to the right and you’re connected to an active dial tone system, when it’s on the right, you will hear dial tone and you’ll be able to actually dial a phone number.

How do you connect about set to a 66 block?

On my Buttset, I have actually zip tied in a standard phone cord. As you can see, I’ve just zip tied it in so they do not come that way. But I’ve done it so that I have the option of using the alligator clips or using a standard phone plug.

When it comes to a 66 block, obviously, we’re going to use alligator clips.

So you want to make sure on your Buttset side, that you’re using the alligator clips connector. Going to switch to our alligator clips connector. And then I’m going to connect this and you’ll see that there are little bitty openings here

kind of c-shaped openings on each side that allows you to go right on these clips.

You can do one that way, and it really doesn’t matter which one you put on top, which one you put on bottom, and you’ll do the second one this way.

So as you can see, the curvature keeps them from touching each other. That way you don’t short out your signal. And as we can tell right now, I’m getting signal through my butt set.

So if that was my dial tone, I would have dial tone all the way through to my butt set.

you can actually just do a temporary touch. If you’re just hunting for dial tone, you can touch here and here.

I’ve got the dial tone. Obviously on my bridge clips, I’ve got dial tone. All the way over here, I have dial tone so I can just touch them as well.

The other way you can do this is if your cable is obviously going to pieces of equipment, you don’t want to cut it to be able to test it.

So the alligator clips allow you to split this out in the middle and put on your alligator clips with your bed of nails. So I’m going to put this one on. Squeeze that down. And again, these can’t touch or it’ll kill your signal. So keep them separated.

Now you can see that my theoretical dial tone has made it all the way from the telco,

through my bridge clips, to the other side.

If you have several devices that are connecting to the same POTS line, then you’re going to need more connectors than what you have available here.

in theory you can have the telco punched here. You could put an internal set of wiring on this one and another set of wiring on this one and another on this.

So you could theoretically have three different devices connected to the same telephone company source.

If for some reason you had more lines needed, then you would have to do a cross connect and you can create daisy chains using the block.

let’s say we wanted to actually go down to the bottom of the block and connect additional devices so we can come all the way to the bottom.

Punch this down here

Now with our bridge clips on our signal will now come into here and be live on all of these pairs. And then we’ll actually follow this wire down to the bottom of our block. And these pairs will be active. And if we wanted to, we put bridge clips on it and it can make all of these active.

So right now. Okay, good live signal here. And I’ve got good signal here. And I have no powerful signal here, just a ghost signal.

once I put my bridge clips down here,

then I have solid signal all the way across the block.

There’s another form of daisy chaining.

You’ll see a lot of older phone systems that actually have a daisy chain in place. So they will bring this signal down and they will actually wrap it back like this. And there could be a dozen of these. There can be two or three of them. You can just go on and on.

I don’t have the proper blade, so I’m trying to be gentle with this. There’s a secondary blade that has no sharp edge on it. And so it would simply push this down without actually cutting it. Because when you’re making a daisy chain, you obviously don’t want to cut it. So I’m just gently doing this for illustration purposes.

So by creating this daisy chain, then you can activate multiple sets of pins.

So we obviously have our ghost signal, but when we touch there, we have a really strong signal. When we touch the set, we have a really strong signal and it carries all the way down to the bottom of the block.

So your goal in this is always to identify where is the telco coming from, where is the internal wiring going to. And if you come into it in this situation and everything’s already wired up, you’re going to get dial tone on the left side and the right side

If you need to determine which side is actually going to the telco, then just remove your clips and then test for dial tone. If your dial tone is over here, you’re telcos on this side for dial tones over here that is on this side.

POTS is pretty simple because it’s just a dial tone.

It’s one phone number. Typically it’s on one set of pins, maybe daisy chain a little bit.

Digital phone system’s

add some other complications to it, which I’m not going to get into in this video, but at least in this regard, you will understand the basics.

My goal with Field Tech Academy is to help aspiring technicians see what they can do, and to help experienced technicians have higher performance. If you got value today from what I shared, please like the video and subscribe to the channel so that you can learn more about how to be an independent field tech. Don’t forget to check out our website at Field Tech

I offer one on one coaching as well as some other products that can accelerate your quest to become self-employed as a technician. As always, let’s get you out in the field making money. I’ll see you in the next video.

Leave a Comment

Your email address will not be published. Required fields are marked *