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  1. I'm not even sure what category to place this post in, as it's not about capturing a signal, just about the signal specification itself. I hope this post doesn't get deleted for being off topic in this section.

    Here's the actual content of this post:
    I just bought a copy of the EIA-170 standard from https://standards.globalspec.com/std/773792/EIA-170 and was reading it, to see how much it differed from an NTSC spec found here http://www.dxdlw.com/bbsupfile/2012/02/10/1734201163/SMPTE 170M-2004 Composite Analog ...plications.pdf

    It turns out that the 1V P-P specification for NTSC (which covers the full 140IRE range from -40IRE at sync to 100IRE at reference white, and ignoring the chroma carrier), is different from the EIA-170 standard. In the EIA 170 standard, it's supposed to be 1V between blanking level and reference white, which is just a 100IRE range, not the full 140IRE range. Interestingly, this means that a video signal using the EIA-170 standard should have a 1.4V P-P range for the full 140IRE range, not a 1V P-P range.

    I wonder how compatible modern equipment is with this older standard. If I bought an old EIA compliant video camera on Ebay, with a 1.4V P-P range, and used it on a modern TV with composite video input (which is NTSC compliant) that expects an 1V P-P range, would it damage the TV?
    Last edited by Videogamer555; 4th Jun 2022 at 13:59. Reason: fixed second link
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  2. Member Cornucopia's Avatar
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    No. It is different but like the difference between 30FPS and 29.97FPS, it isn't different enough to not maintain compatibility. Which is why they went with it.

    You wonder about B/W cams & signals driving a color screen/electronics, or vice-versa, but those both peacefully coexisted for over 40 years.

    Perhaps you are misinterpreting the information?


    Scott
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  3. Originally Posted by Cornucopia View Post
    No. It is different but like the difference between 30FPS and 29.97FPS, it isn't different enough to not maintain compatibility. Which is why they went with it.

    You wonder about B/W cams & signals driving a color screen/electronics, or vice-versa, but those both peacefully coexisted for over 40 years.

    Perhaps you are misinterpreting the information?


    Scott
    I know that more modern signal sources tried to be compatible with older viewing equipment, but I didn't know that modern viewing equipment (especially consumer grade equipment) tried to be compatible with older video sources. There's no reason to expect that a person with a modern TV would also have access to an old 1950s era video camera (especially since these were big clunky things that were very expensive and only owned by professional studios). But it might be assumed logically that not all people had gotten rid of their old B&W TVs, so that when a more modern color TV broadcast occurred it should be designed to be compatible with older B&W TVs.
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    Originally Posted by Videogamer555 View Post
    I know that more modern signal sources tried to be compatible with older viewing equipment, but I didn't know that modern viewing equipment (especially consumer grade equipment) tried to be compatible with older video sources. There's no reason to expect that a person with a modern TV would also have access to an old 1950s era video camera (especially since these were big clunky things that were very expensive and only owned by professional studios). But it might be assumed logically that not all people had gotten rid of their old B&W TVs, so that when a more modern color TV broadcast occurred it should be designed to be compatible with older B&W TVs.
    Composite video was invented in the 1950s but the connection wasn't used for consumer viewing equipment until much later. I don't recall seeing any RCA connections for composite video and stereo audio on TVs until sometime in the 1980s.

    Consumer TVs only had connections for antennas for a very long time, so yes, maintaining compatibility was only necessary for broadcasts. Initially. there were 2 screws for connecting a VHF antenna, later 2 more screws were added for connecting a UHF antenna, and later still, all the screws were replaced with just one RF coax connection for connecting either cable service or an antenna after cable-ready TVs became available.

    However, I think Scott is probably correct regarding compatibility.
    Ignore list: hello_hello, tried, TechLord, Snoopy329
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  5. Member Cornucopia's Avatar
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    RCA for composite was introduced in the 70s after successfully being used for audio for a while. Prior to that, BNC was used on pro equipment when industry standard interchange was necessary (sometimes the setup was all one manufacturer, so they could used whatever proprietary connection they liked).
    Prior to the 70s, there wasn't any consumer video worth mentioning.*

    Scott

    *(exceptions such as phillips or sanyo formats, or sony open reel or cartridge formats, were either expensive or very poor quality or both, and consumer video didn't take off until beginning with 3/4" Umatic, and then really Betamax and VHS).
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  6. Originally Posted by usually_quiet View Post
    Originally Posted by Videogamer555 View Post
    I know that more modern signal sources tried to be compatible with older viewing equipment, but I didn't know that modern viewing equipment (especially consumer grade equipment) tried to be compatible with older video sources. There's no reason to expect that a person with a modern TV would also have access to an old 1950s era video camera (especially since these were big clunky things that were very expensive and only owned by professional studios). But it might be assumed logically that not all people had gotten rid of their old B&W TVs, so that when a more modern color TV broadcast occurred it should be designed to be compatible with older B&W TVs.
    Composite video was invented in the 1950s but the connection wasn't used for consumer viewing equipment until much later. I don't recall seeing any RCA connections for composite video and stereo audio on TVs until sometime in the 1980s.

    Consumer TVs only had connections for antennas for a very long time, so yes, maintaining compatibility was only necessary for broadcasts. Initially. there were 2 screws for connecting a VHF antenna, later 2 more screws were added for connecting a UHF antenna, and later still, all the screws were replaced with just one RF coax connection for connecting either cable service or an antenna after cable-ready TVs became available.

    However, I think Scott is probably correct regarding compatibility.

    I may be mistaken, but I think I remember seeing a TV once that had an F-type jack for VHF antenna but 2 screw terminals for the UHF antenna.
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  7. Originally Posted by Cornucopia View Post
    RCA for composite was introduced in the 70s after successfully being used for audio for a while. Prior to that, BNC was used on pro equipment when industry standard interchange was necessary (sometimes the setup was all one manufacturer, so they could used whatever proprietary connection they liked).
    Prior to the 70s, there wasn't any consumer video worth mentioning.*

    Scott

    *(exceptions such as phillips or sanyo formats, or sony open reel or cartridge formats, were either expensive or very poor quality or both, and consumer video didn't take off until beginning with 3/4" Umatic, and then really Betamax and VHS).
    BNC is still used for composite video output on security cameras. Not sure why they don't use RCA now, but it seems that BNC stuck with the security camera industry. Same for analog scientific cameras found on Edmund Optics website. And BNC is now used for SDI, a professional digital video connection. Consumer grade digital video cameras use HDMI. Not sure why HDMI is only used on the consumer side, and SDI is only used on the professional side.

    There also was an older style of connector for consumer analog video cameras. I remember it being a round 10-pin connector. I think of the Hirose type. It had power, video, audio, and remote control signals all in the same cable. It connected to either a VCR with a 10-pin connector, for recording directly to a VHS tape, or alternatively could be powered by a dedicated power supply, which also had a breakout board in it that output the audio to RCA, and composite video to a UHF-type connector (it's called UHF even though it has nothing to do with the UHF band of the RF spectrum). For some reason its video output used this much less common UHF type connector, instead of the more common BNC or RCA type of connectors. Though I think I've seen some of these power supplies on Ebay with a UHF-to-RCA cable, I'm not sure if those were custom/modified cables added by the seller, or if they actually used such cables on those old camera power supplies back at the time they were the currently used type of equipment.
    Last edited by Videogamer555; 7th Jun 2022 at 17:59.
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  8. Member Cornucopia's Avatar
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    I may be mistaken, but I think I remember seeing a TV once that had an F-type jack for VHF antenna but 2 screw terminals for the UHF antenna.
    Yes, that was another variation.

    BNC is still used for composite video output on security cameras. Not sure why they don't use RCA now, but it seems that BNC stuck with the security camera industry. Same for analog scientific cameras found on Edmund Optics website. And BNC is now used for SDI, a professional digital video connection. Consumer grade digital video cameras use HDMI. Not sure why HDMI is only used on the consumer side, and SDI is only used on the professional side.

    There also was an older style of connector for consumer analog video cameras. I remember it being a round 10-pin connector. I think of the Hirose type. It had power, video, audio, and remote control signals all in the same cable. It connected to either a VCR with a 10-pin connector, for recording directly to a VHS tape, or alternatively could be powered by a dedicated power supply, which also had a breakout board in it that output the audio to RCA, and composite video to a UHF-type connector (it's called UHF even though it has nothing to do with the UHF band of the RF spectrum). For some reason its video output used this much less common UHF type connector, instead of the more common BNC or RCA type of connectors. Though I think I've seen some of these power supplies on Ebay with a UHF-to-RCA cable, I'm not sure if those were custom/modified cables added by the seller, or if they actually used such cables on those old camera power supplies back at the time they were the currently used type of equipment.
    BNC is still used for a number of non-consumer applications, pro-, security-, and military- being among them. The reason BNC is used over RCA (both for analog - composite and component - and digital - via SDI) is that is it LOCKABLE (or rather, more accurately: LATCHABLE). Similarly on the audio side, this is often why pro applications require use of XLR & Speakon connectors. If things are mobile or in a difficult environment or have lots of activity around it, you do not want the connection to come loose.

    Those Hirose-style connectors were proprietary and specific to old school umbilical type cameras (with a carry bag for the portable VTR - the weight of that combo - some of them ~75lbs - caused first time I ever strained my back!), prior to the rise of the all-in-one "camcorder". Those cables were common for a certain manufacturer along certain production lines, but otherwise there was no commonality so they were not very interchangeable.

    ********
    But back to the original topic, all that stuff was designed to be backward and forward compatible (B/W analog vs. Color analog). And it was, regardless of whether one used a camera or other device as a source, and a TV or other device as a sink (as long as one understood that once the signal was/became B/W, it would remain that way through the rest of the chain).


    Scott
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  9. Originally Posted by Videogamer555 View Post
    I'm not even sure what category to place this post in, as it's not about capturing a signal, just about the signal specification itself. I hope this post doesn't get deleted for being off topic in this section.

    Here's the actual content of this post:
    I just bought a copy of the EIA-170 standard from https://standards.globalspec.com/std/773792/EIA-170 and was reading it, to see how much it differed from an NTSC spec found here http://www.dxdlw.com/bbsupfile/2012/02/10/1734201163/SMPTE 170M-2004 Composite Analog ...plications.pdf

    It turns out that the 1V P-P specification for NTSC (which covers the full 140IRE range from -40IRE at sync to 100IRE at reference white, and ignoring the chroma carrier), is different from the EIA-170 standard. In the EIA 170 standard, it's supposed to be 1V between blanking level and reference white, which is just a 100IRE range, not the full 140IRE range. Interestingly, this means that a video signal using the EIA-170 standard should have a 1.4V P-P range for the full 140IRE range, not a 1V P-P range.

    I wonder how compatible modern equipment is with this older standard. If I bought an old EIA compliant video camera on Ebay, with a 1.4V P-P range, and used it on a modern TV with composite video input (which is NTSC compliant) that expects an 1V P-P range, would it damage the TV?


    To anybody who was reading that post and tried to click on my second link, I just tested it today and it's now a broken link. Apparently the PDF file was deleted from there (a place it literally had been for years), so I'm uploading it here as an attachment here.
    Image Attached Thumbnails SMPTE 170M-2004 Composite Analog Video Signal--NTSC for Studio Applications.pdf  

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  10. It looks like the thumbnail generator for PDF files didn't work well on this one, because it's all black in the thumbnail here, but the actual PDF file is just fine, and didn't become corrupted when I uploaded it (I downloaded it from here to verify that).
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  11. Originally Posted by Cornucopia View Post
    BNC is still used for a number of non-consumer applications, pro-, security-, and military- being among them. The reason BNC is used over RCA (both for analog - composite and component - and digital - via SDI) is that is it LOCKABLE (or rather, more accurately: LATCHABLE). Similarly on the audio side, this is often why pro applications require use of XLR & Speakon connectors. If things are mobile or in a difficult environment or have lots of activity around it, you do not want the connection to come loose.
    There is also another important reason for using BNC - BNC have defined impedance where RCA doesn't have specified/defined impedance and impedance vary between RCA connectors manufacturers...
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