Patch Bay

The patch bay can look very confusing if you don't know what it's all about. But it works similarly to routing switcher (see that article below). Its main job is to provide access to inputs and outputs of the facility.

Everyone patch bay i've encountered (I'm not sure if everyone does it the same) has the signal flow the same way: FROM the top TO the bottom. In more technical terms, the top is the output and the bottom is the input for two corresponding patch bay nodes, meaning in the same column.

Here is what a patch bay looks like with a few cables plugged in:

Here is what a patch bay looks like lots of cables plugged in:

 As you can see, patch bays can be very helpful but they can get out of hand if no one maintains them to see if connections are still required. If a connection made with a patch bay becomes a permanent connection, it is a good idea to make that connection permanent behind the rack, clearing up space for more temporary fixes.

This is what the back of a professionally installed patch bay looks like.

Now for a closer look, here is what the nodes look like. Here you can see that we have a DA (distribution amplifier) hooked up to the patch bay.

So how this would work is, you plug a source, say a camera, into one of the DA SDI INs, which would be on bottom, they that feed becomes availible as an output on the top row for all the designated nodes.

Here is a more basic example: we have our SDI ROUTER OUTPUTS on top which you can see feed our CCU CAMERA RETURN INPUTS. So with a quick look at the patch bay you can see that Router Output 12 feeds Camera 12's Return. You can also see a cable coming out of #09, we have stolen that output for something else, so Camera 9 will not be getting it's return. You can also think of it as, we are sending Camera 9's feed somewhere else.

When nothing is plugged into either the output or input that pair is considered Normal. In the image above the only thing that is not normalized is the #09 SDI ROUTER OUTPUT. So for example, SDI ROUTER OUTPUT 10 feeds Camera 10 return, unless interrupted.

As you can see the patch bay is very instrumental to the operation of the facility for quick, temporary changes in the facilities signal flow.

I hope this helps, leave any corrections, comments or questions below :)

Master Clock/Sync Pulse Generator

Another one of the most important parts of the production facility is the Master Clock/Sync Pulse Generator (SPG), also know as "Reference".

As we saw with the Routing Switcher, a lot of the equipment works in tandem with each other. To ensure everything works together, "at the same time", you need it all to have a reference to something, which is the function of the  Master Clock/SPG.

Let's suppose we did not have a Master clock/SPG. At the very visually obvious level, our cameras would not be synchronized and would thus not resolve their images at the same time, so when we switched between cameras there would be jump in the image. There would also be discoloration due to the lack of phase synchronisation. The record and playback decks would create lines in the picture because it would not resolve the bottom of the image at the bottom of the screen.

So as you can see, it would be pretty catastrophic if we did not have reference to our equipment.

There are a multitude of ways to configure the output of your SPG. At our facility we use HD Tri-level SMPTE ST 274 1080i/59.94.

We are using an Evertz 5601MSC Master Clock/SPG.

As you can (kind of) see, sorry for the bad quality picture, we use 2 MC/SPGs with an Automatic Changeover. This does just what it sounds like. If one of the Master clocks should fail, the other one is automatically assigned to take over sending reference to all the equipment. 

Back of Both MC/SPGs and Automatic Changeover

As you can see, on the back it uses almost all BNC connections, as the Routing switcher does, even for DARS (Digital Audio Reference Signal), with the exception of a few XLR for LTC (Longitudinal Time Code) outputs.

I feel like this post got a little bit out of hand, it was a little harder explaining this than I thought. I may end up editing it later. But for now, I hope it helps. :)

Please leave any comments, corrections or questions you have.

Next up: The Patch Bay

Routing Switch/Router

I debated a little bit on where to start, but I think i'll start at what I think the heart of the system is, the Routing Switcher. Where I work we use a Harris Platinum routing switcher with a maximum I/O (Input/Output) of 512x512. However, we don't use nearly that many. It occupies 28 RU (Rack Units). The Routing switcher is the piece of equipement that almost everything other pieces plugs in and/or out of. It works kind of like a huge DA (Distribution amplifier) with assignable In and Outs, able to take any one signal and distribute it as many places as needed.

Back of Routing Switcher

Front of Routing Switcher

Routing Switcher Opened

The Router is made up of different modules. Since we use HD-SDI at this plant, that is what I'll be implying for video signal unless stated otherwise. We use:

-20 Video Input cards with 8 inputs each (160 In)

-28 Video Output cards with 8 inputs each (224 Out)

-4 Multiviewer units with 4 designable layouts each (16 Multiviewers)

-5 AES Audio Input cards with 16 inputs each (80 In)

-6 AES Audio Output cards with 16 outputs each (96 Out)

I think I'll wait to talk about audio and try to do it as a whole, as I am less comfortable talking about it compared to video.

As far as the inputs go, a large part of that comes from the production switcher (I'll cover that in another post). Some things that are inputs include: Cameras, program feeds (clean and dirty), previews, playback decks, character generators, etc.

Outputs could be: Monitors, Camera returns, Record decks, and tie lines to name a few.

And of course it has a reference signal coming in to sync in to the rest of the equipment in the facility.

I think that will do it for now, I just wanted to go over some of the basics of it.

Next up, the Master Clock.

As always, comments and questions are always welcome.

An Intro

This blog is mostly for me to keep sharp at my fairly recent job as a Production Engineer for a Spanish language network.  I'll start with the basics; all the equipment used, what they do and how they interact with other pieces of equipment.  After that, we'll see I guess lol. I hope we all can learn a little something. Enjoy :)

Comments and Questions are encouraged.