[Jeff Hartman]

Two things come to mind:

1) An integrated beltpack that incorporates intercom, tally, and several remote control circuits. This would have rechargeable batteries, and operate through a WiFi network; each pack would have its own IP address, so you can move throughout a facility wirelessly. Since the switchers are already on the network, it should be pretty easy to incorporate tally and control into this.

2) An HD character generator on an OpenGear card with capabilities at least similar to the Chyron digital PC Codi. It too would run from a network connection, and it should be able to either self-key over incoming HD-SDI, or lock to an external reference and produce key and fill signals to hook to a production switcher. Squeezeback could also be handy. A device like this would be invaluable for television stations that need to insert emergency graphics or station branding.

Oh, and one other thing: it would be really great if any new products would actually do the functions they are billed as having. I am still waiting for my up-down-cross converter cards to pass closed captioning, and we’re coming close to a year now.

— Jeff

[Jeff Hartman]

There are really two issues to tackle: first, how to connect physically to the BMD adapter; second, how to create a practical tally light.

First, the connections: while you can certainly connect directly to the 25-pin D connector, many people find a screw terminal easier to use. Phoenix Contact makes an adapter that has a 25-pin male connector and a numbered screw terminal for each pin. You can get it from Digikey (https://www.digikey.com), and their part number is 277-2010-ND. You will also need a short male-to-female 25-pin cable to connect this to the BMD box; Digikey’s AE9865-ND will do the job, and is two meters long. The adapter and cable together come to less than $65, plus tax and shipping, and give you easy access to every pin without soldering… and this makes it easy to add other wiring later without disassembling the D connector.

Now, for the light itself. The relays in the BMD tally interface can’t switch a lot of current, so incandescent lamps are probably out. LEDs are the most obvious alternative, but don’t come with convenient provisions for mounting or connection. More important, you don’t drive LEDs directly from a voltage source as one would with a traditional light bulb; you need to provide current limiting, usually in the form of a resistor that you size to produce a certain amount of current (10 milliamps, say) given a certain source voltage.

An easier solution that we are using comes from NAPA auto parts: it’s an LED truck marker light that runs from anything from about 8 through 16 volts, is easy to mount, and has all of the necessary current limiting built in. You just treat it like any ordinary light bulb. Their part number is LIT 2150, and the whole thing costs less than twelve dollars. You will find two wires on the back: one has a free end, the other is connected to one of the screw holes. You will want to disconnect (cut) that second wire so it isn’t tied to the mounting screw.

The last piece you need is a 12-volt DC power supply — Digikey, for example, sells a wall-wart made by CUI that will drive as many of these truck lights as you want for under $8: their part number is T983-P5P-ND. You just need to cut off the barrel plug on the end of the zipcord. One of the two wires will have some sort of marking on it — often a stripe — so you can tell them apart. If you have a meter handy, you can check which is positive and which is negative; if not, I find that usually the striped wire is positive on CUI supplies. Connect the negative (unstriped) wire to pin 25 on the adapter, and set the positive wire aside for a moment.

For each truck light, just run a single pair cable — even audio wire will work — from the tally adapter out to the camera (or whatever). At the light end, connect the wire that had been the ground (screw hole) to the black wire in the cable, and tie the longer wire (positive) to the red wire. Back at the tally interface, connect all of the red wires (light positive) to the positive wire from the power supply; a small wire nut will do fine. Connect the black wire (light ground) to the appropriate tally output from the adapter: TALLY 1 is pin 23, TALLY 2 is pin 22, TALLY 3 is pin 21, and so on; TALLY 8 on pin 16.

All this is actually a lot easier than it sounds, and you can tally all eight sources for somewhere around $150.

Run wild!

— Jeff

[Jeff Hartman]

I’ve been running the interface with one of our TVS units since last November, and you’re right: the tally indeed works very well. It’s worth pointing out, though, that the GPI portion of the interface doesn’t actually do anything — at least with the Television Studio. That’s a pity, because being able to assign GPIs to various panel functions would be incredibly useful.

— Jeff

[Jeff Hartman]

The TVS has both SDI and HDMI outputs. The first is the industry standard for professional digital video and the second is something of a “pro-sumer” standard, as well as a common interface for monitors and projectors. So the TVS does in fact work just fine with an overwhelming majority of digital equipment out there.

If your application requires analog outputs, perhaps an analog switcher would be a better fit than the TVS, which is fundamentally digital.

— Jeff

[Jeff Hartman]

Yes, I am aware of the mechanics of converting between 608 and 708 captions. The specific problem here is that the card performs proper conversion between some formats and not others. They acknowledged the problem back in December and said they were working on it. Half a year later, the problem is still not resolved.

Even if they are having technical problems making the product work correctly, that doesn’t explain why they haven’t updated the manual in three years so that it at least covers the products for which the document is downloaded.

If I seem annoyed, it’s because frankly, I am. When one of my stations is out of technical compliance for whatever reason, I am expected to solve the problem promptly or be subject to government fines or sanctions. The FCC isn’t going to care that we aren’t transmitting closed captions because Blackmagic can’t get their firmware fixed; we are ultimately held accountable. I wish that if BMD is going to target the broadcast market, that they would either take technical standards seriously enough to make sure their gear is fully compliant with relevant standards, or else give sufficient specifications for their products so that we can accurately discern whether they will actually perform the task we need to accomplish.

— Jeff

[Jeff Hartman]

Just to clarify: when the SDI feed goes away, do you get one pop and then silence, or is it continuous noise?

A single pop isn’t necessarily a surprise: the D>A converter will be going almost instantly from its last known value to zero volts. But that should be the end of the noise (until the SDI comes back on).

— Jeff

[Jeff Hartman]

[Chuck Pullen] “Maybe Blackmagic will stop being “elitist” and start making their products to play nice with others?”

I’m not sure it’s fair to say they’re being elitist: from a purely technical point of view, a four-wire system can outperform a two-wire system in many respects, and it’s consistent with how the signals are transmitted over the fiber. Adding two-wire conversion would seriously degrade the performance when linking multiple units together, because there’s a practical limit to how much gain you can create in each direction without making the system unstable and breaking into feedback.

As far as interfacing goes… the BMD actually interconnects really well into a system like our RTS Adam, or our Telex wireless base stations. I’ve been installing and designing intercom systems for years, and the big problem for every single one is interfacing to a dissimilar system — especially when you have to tie into things like phone lines, camera base stations, wireless systems, and the like.

I suppose I should be grateful: at least it’s a perverse sort of job security. (grin)

— Jeff

[Jeff Hartman]

I was rather surprised to see such a snarky response to fairly straightforward replies. Yes, Blackmagic gear is low-budget… but RTS decidedly isn’t. For a facility that already has a full RTS system and wants to tie it into a new piece of BMD equipment, citing an RTS interface as a known-good solution is certainly not unreasonable.

Having said that, if low price is the only constraint, it’s quite straightforward to build a hybrid circuit with two transformers (two Triad TY-300P, for instance), one 560 ohm resistor, and one 100 ohm potentiometer. This will achieve a fairly decent null between the BMD incoming and outgoing audio (set the potentiometer to minimize the sidetone at the camera end). Total parts cost should be under $20 from Digikey.

If you take a look at the description of the double transformer hybrid on Wikipedia’s “Hybrid Coil” page, “W” would connect to the RTS coupling jack, “X” would be the BMD send audio (with an attenuator to drop it to mic level), “Z” would be the BMD receive audio, and “Y” would be the 560 ohm resistor in series with the 100 ohm potentiometer. The dots in the drawing indicate the polarity for each transformer winding, and it’s essential to observe correct polarity or else the hybrid won’t work correctly.

The downside is that this is a very rudimentary approach. Aside from needing some skill to build and some effort to tweak so it works decently, it lacks the automatic nulling, ducking, and dynamics control that you get with an RTS interface.

One other observation about intercoms in general: both two-wire and four-wire systems have been around for a very long time, and each has its advantages. The RTS TW system is two-wire; the digital RTS Adam is four-wire, and I happen to have installed both here. I see no significance in Blackmagic’s design approach beyond the fact that since their system transmits and receives separately, the link is intrinically four-wire; there is nothing to be gained and a lot to lose by adding four-wire to two-wire conversion if you don’t actually need it.

— Jeff

[Jeff Hartman]

Quote: “F I L E – B A S E D Processing is the workflow for the 21st century.”

Certainly for post-production… but it’s not terribly useful for live origination and broadcast, even in the 21st century. Methinks there is still a place for both. (grin)

Jeff Hartman
Engineering Project Manager
Newport Television, Northeast

[Jeff Hartman]

What you are actually doing here is interfacing a two-wire intercom (the RTS) to a four-wire system (the Blackmagic). The difference is this: a two-wire system has bi-directional audio, like a phone line; in a four-wire system one pair sends audio out while the second pair receives incoming audio.

The “textbook” solution, if you are using an RTS system, would be to use their SSA-324 system interface. The connection would be like this:

1) Plug the RTS party line XLR feed into the SSA’s 2-wire I/O jack;

2) Connect the headphone out from the Blackmagic interface to the SSA’s 4-wire in;

3) Connect the SSA’s 4-wire out through an attenuator pad to the Blackmagic interface’s mic in (the attenuator drops the SSA’s line level down to mic level).

The SSA has two sections (A and B), so you can use this to separately tie to two Blackmagic converters.

Regards,

Jeff Hartman
Engineering Project Manager
Newport Television, Northeast