There seems to be a lack of broadcast engineering discussion forums online, so this new forum is a good initiative... let's give it a try.

I'm designing a low-cost HD live-switching system for a church; we'll be using 3 HVX200 cameras and the Panasonic AV-HS400 switcher with component HD option. For wiring, instead of messing with out-of-budget multicore, triax or fiber cables, I'll be taking a premade snake which runs multiple 3GHz coax, audio, and power wires.

What I want to figure out is tally light support. The Datavideo TB5 (http://www.datavideo.us/products/TB_5_main_page.htm) or its rackmount brother, the RP-7, is a complete kit that takes a D-Sub connector from a switcher and includes 4 tiny strap-mounted tally lights (model TD1) that I can put on the cameras, all ready to go. The question is, will it work?

• The AV-HS400 has a D-sub 15-pin connector with 8 pins labled IN1-IN8 that are tally outputs(?), an Enable signal, and a common ground. The maximum supported dielectric strength is 24VDC and 50mA. [Diagram]
• The TB5 is designed to connect to Datavideo's own switcher, and they were unwilling to reveal its electrical characteristics, so all I have is the switcher's pinout and basic diagram.
• I intend to run the signal through 150 ft. of 26 AWG (7x34) Stranded TC wire, rated at 38.5 Ω/Mft.
  

I can easily make the right D-Sub cable to accommodate the pinouts, but I want it to work, and I don't want to overload anything...  It seems to me like the TB5 takes data signals and applies power to drive the LEDs, while the AV-HS400 is designed to drive small lights directly. I'd appreciate your insight.

Looks like it should work fine- provided the tally circuit does not overload the switcher capacity.

I have built a tally light system like this in the past with some simple relays and power supply- maybe $50 in parts and a couple hours of labor.  I did this instead of a pre-built system to have full isolation of two seperate tally light circuits, one 12VDC LED's and the other contact closures.  The LED's had up to 250 foot of CAT5 wire runs- system worked well.

 (Gawd I don't have time for more forums!  But here goes...)

 
It appears that both systems are intended to work the same way.  The Pana switcher tally connection is a current-sinking ground closure, so it passes the LED current to ground through a transistor which completes the circuit.  The power for the LED has to come from outside the switcher.  The Datavideo switcher circuit looks like the same thing.  The TB5 is probably just a power supply and distribution box for the light wiring.  I'm guessing it would work fine--a single LED should not pull anywhere near the 50mA limit of the Pana connections.  You might want to use 24 or 22ga wire for the tally runs to keep the loss in the cable to a minimum.

 My only concern is that the TB5 really does connect to the Datavideo switcher via that same DSub with those signals.  The cable they provide is called an "RS-232" cable, which implies a serial data connection, but I think it's just a 9-pin straight-through cable.  The signals shown on the switcher pinout are not "data" they are just analog voltages (or ground connections, as it were).
 

 
-- Eric Wenocur
Lab Tech Systems