Editing VGA connector (section)

== Electrical design ==
All VGA connectors carry [[Analog television|analog]] [[RGBHV]] (red, green, blue, [[horizontal sync]], [[vertical sync]]) video signals. Modern connectors also include [[Video Electronics Standards Association|VESA]] [[Display Data Channel|DDC]] pins, for identifying attached display devices.

In both its modern and original variants, VGA utilizes multiple [[Vertical scan rate|scan rate]]s, so attached devices such as monitors are [[Multisync monitor|multisync]] by necessity.

The VGA interface includes no affordances for [[hot swapping]]{{cn|date=April 2025}}, the ability to connect or disconnect the output device during operation, although in practice this can be done and usually does not cause damage to the hardware or other problems. The VESA DDC specification does, however, include a standard for hot-swapping.<ref>{{Cite book |title=VESA DDC/CI Standard Version 1.1 |year=2004 |pages=31 |quote=DDC/CI supports hot plugging, provided the display can detect a disconnection of the video cable}}</ref>

=== PS/2 signaling ===
In the original IBM VGA implementation, refresh rates were limited to two vertical (60 and 70&nbsp;Hz) {{dubious-span|reason=this claim does not seem to be in the cited source (though I would not exclude the possibility OP may have misread the source, or if I'm misreading it, tell me how); claim originally added here: https://en.wikipedia.org/w/index.php?title=VGA_connector&diff=prev&oldid=973364678|and three horizontal|date=May 2024}} frequencies, <span class="cleanup-needed-content" style="padding-left:0.1em; padding-right:0.1em; color:var( --color-emphasized, #595959 ); border:1px solid #DDD;">all of</span> which were communicated to the monitor using combinations of different polarity H and V sync signals.<ref name="IBM PS/2">{{Cite book |url=http://classiccomputers.info/down/IBM_PS2/documents/PS2_Hardware_Interface_Technical_Reference_May88.pdf#page=492 |title=IBM Personal System/2 Hardware Interface Technical Reference |chapter=Video Subsystem (Type 1) |pages=13.99–13.100 |archive-url=https://web.archive.org/web/20180514201314/http://classiccomputers.info/down/IBM_PS2/documents/PS2_Hardware_Interface_Technical_Reference_May88.pdf#page=492 |edition=First |publisher=[[IBM]] |date=May 1988 |archive-date=14 May 2018 |access-date=16 February 2021}}</ref>

Some pins on the connector were also different: pin 9 was keyed by plugging the female connector hole, and four pins carried the monitor ID.<ref name="IBM PS/2" />

With the implementation of the VESA DDC specification, several of the monitor ID pins were reassigned for use by DDC signaling, and the key pin was replaced with a +5&nbsp;V DC output per the DDC spec. Devices that comply with the DDC host system standard provide {{nowrap|5 V ± 5%}}, from 50{{nbsp}}mA to 1{{nbsp}}A.<ref>{{Cite book |title=VESA Enhanced Display Data Channel Standard Version 1.1 |publisher=[[Video Electronics Standards Association]] |date=24 March 2004 |page=18}}</ref>

=== PS/55 signaling ===
The [[IBM Personal System/55|IBM PS/55]] Display Adapter redefined pin 9 as "+12V", which signals the monitor to turn on when the system unit is powered on.<ref>{{Cite web |title=Japanese Display Adapters |url=https://ardent-tool.com/PS55/video/ |access-date=2023-02-05 |website=Ardent Tool of Capitalism}}</ref>

=== EDID ===
{{Further|Display Data Channel|EDID}}
In order to advertise display capabilities [[VESA]] has introduced a scheme to redefining VGA connector pins 9, 12, and 15 as a serial bus for a [[Display Data Channel]] (DDC).<ref>{{Cite web |title=Understanding EDID - Extended Display Identification Data |url=https://www.extron.com/article/uedid |access-date=19 May 2022 |website=Extron |language=en}}</ref>