CurtPalme.com Home Theater Forum

[noos@xp37+]

Hello,

I need a info about this signal: VGA 640 x 480, H&V - TTL, analog 0.7V P-P, 75 ohms.

What is TTL? I think I have a switch that can output it. What about analog 0.7V P-P?

Thanks

Marc

[barclay66]

Hi,

The description reminds me of the standard parameters of a computer's VGA display connector.

TTL usually stands for Transistor-Transistor-Logic. It's the kind of logic gates which most commonly is referred to as the 74-series. Those circuits operate at a supply voltage of 5V and only know the logic states 0 (off) and 1 (5V). So expect to get a 5V digital (impulses) signal at the H and V sync lines.

0.7V P-P refers to the common analog video signal level (widely used in many applications). P-P stands for Peak to Peak and describes the difference in voltage between the minimum and the maximum of the analog signal waveform. Expect to find this type of signal on each color line (RGB). It's analog so that an almost unlimited number of colours can be displayed. 75 ohm defines the impedance for these lines and is the identical to the value of the resistors that You will find at beginning and end of a signal path (resistor connected between line and ground, very common too).

As it states that it is VGA I would expect around 31.5 kHz for H-sync and 60 Hz for V-sync. You could as well call it 480p.

Regards,
barclay66

[noos@xp37+]

Thanks, and what a description! You really must have a good background for dealing with analog devices like crt projectors....

So is TTL the standard signal? I ask because I want to run this device (link below) without the controller box - so I will have to drive the right pins of the cable with the right kind of signal. I think I remember several CRT projector manuals that had mentioned TLL as an extra kind of signal that is understood by the projector or not. Sounded to me like a old style of signal, so I guess thats why my Sony crt switcher can be jumpered to output TTL, and the normal option/jumper position is called analog.

So here is the device I try to bring alive:

http://www.mindflux.com.au/products/keo/Proview%2030.pdf


Best regards from FFB

Marc

[barclay66]

Hi,

danke für die Blumen (thank You for the flowers)!

Please don't confuse TTL video with TTL sync signals. TTL video is what the very first PC had (only 8 or 16 colors).

The only thing You need is a normal computer with a regular VGA card and output (Sub-D-15). You set it to 640x480 resolution and connect both with a standard VGA cable.

If You want, You can test it in my "Lab". I have lots of cables and adapters and older PC hardware that we could use to try it out. I live not far away from FFB. PM me for details if You want...

Regards,
barclay66