Why did VHS tapes show a blue screen on the TV when they started up?

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Why did VHS tapes show a blue screen on the TV when they started up?

In: Technology
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That was the VCR, not the tape itself.

It’s the precursor to the HDMI no signal screen. Used to be blue.

That’s not the tape. That’s either the TV or the VCR telling you, “I don’t have anything clear enough to show you right now.”

I remember when that was a new thing. Before that, we saw a black screen with white lines or scrambled black and white dots.

The blue screen was not from the VHS tape, but rather from the VCR.

In many cases, VCRs would be hooked up to the TV with a coaxial (RF) cable. The VCR would generate a NTSC video signal on channel 3 or 4, which you would view by turning the TV to channel 3 or 4. In most of the US channel 3 was reserved (no broadcast signal) for this reason.

When the VCR turns on, there was a desire for it to send some kind of signal to the TV so you’d know it was hooked up right. Otherwise the TV would just show static (if using coax) or a black screen (if using composite).

Thus, the blue screen. Easy to generate without complex circuitry (remember, VCRs were mostly analog devices) and it let you know the VCR was on, you were tuned to the right channel, and things were hooked up correctly.

Later VCRs would then overlay text onto that blue screen or the video image such as PLAY / STOP / etc so you could control the VCR using the screen.