DE-15 (VGA)

DE-15, universally known as the VGA connector, is a three-row, 15-pin D-subminiature connector used for analog video output. Introduced by IBM in 1987 with the PS/2 and its Video Graphics Array (VGA) graphics system, the connector became the dominant standard for connecting computers to CRT monitors and remained ubiquitous on PCs, monitors, projectors, and televisions for over two decades.

The connector is also referred to as HD-15, HD15, DB-15HD, or mini sub-D15. The "DE-15" designation is technically correct — "D" for the D-sub family, "E" for the shell size, and "15" for the pin count — but like the DB-9, the misnomer "DB-15" is frequently encountered.

History

Prior to VGA, IBM PC graphics adapters (MDA, CGA, EGA) used the DE-9 connector to carry TTL-level digital RGB signals to direct-drive CRT monitors. When IBM introduced the VGA standard in 1987, the shift from digital to analog RGB signals required a new connector with more pins to accommodate the three analog color channels, separate horizontal and vertical sync signals, and ground returns for each.

The DE-15 connector used the same E-size D-sub shell as the DE-9 but packed 15 pins into three rows of five using higher-density pin spacing. This "high density" arrangement is why the connector is often called "HD-15."

Some early third-party VGA-compatible hardware (both graphics cards and monitors) initially used DE-9 connectors for analog VGA signals, omitting several pins. This was considered acceptable in the pre-Plug and Play era, but the practice was quickly abandoned in favor of the standard DE-15.

The DE-15 connector remained the primary analog video interface on PCs until the mid-2000s, when digital interfaces — DVI (1999), HDMI (2003), and DisplayPort (2006) — began displacing it. Many modern computers no longer include a VGA output, though the connector remains common on projectors, industrial equipment, and KVM switches.

Design

The DE-15 connector features 15 pins arranged in three rows of five within a D-shaped metal shell. Like other D-sub connectors, the shell ensures correct orientation and prevents reversed insertion. Cable connectors typically have thumbscrews that thread into jackscrews on the panel-mounted socket for a secure connection.

The red, green, and blue analog signals (pins 1, 2, 3) each have dedicated ground return pins (pins 6, 7, 8), which serve as miniature coaxial shields within the connector. However, the short unshielded distance between pins within the connector shell can allow crosstalk between the RGB signals, particularly at higher resolutions and refresh rates. For maximum signal integrity, professional equipment often uses five separate BNC connectors (R, G, B, H-sync, V-sync) instead.

The VGA interface does not natively support hot-swapping, though in practice connecting or disconnecting a VGA cable while equipment is powered usually does not cause damage.

Pinout

DE-15 VGA Pinout (VESA DDC2)

Pin	Function
1	Red video (analog, 0.7Vpp, 75Ω)
2	Green video (analog, 0.7Vpp, 75Ω)
3	Blue video (analog, 0.7Vpp, 75Ω)
4	Reserved (formerly Monitor ID 2)
5	Ground (digital return)
6	Red ground
7	Green ground
8	Blue ground
9	+5V DC (from graphics card, for DDC)
10	Sync ground
11	Reserved (formerly Monitor ID 0)
12	DDC SDA (I²C data) / formerly Monitor ID 1
13	Horizontal sync (or composite sync)
14	Vertical sync
15	DDC SCL (I²C clock) / formerly Monitor ID 3

In the original 1987 VGA specification, pins 4, 9, 11, 12, and 15 were used for Monitor ID bits, and pin 9 was a keying pin (no connection). The VESA Display Data Channel (DDC) standard later redefined several of these pins to support bidirectional communication between the graphics card and monitor, enabling Plug and Play monitor detection and EDID (Extended Display Identification Data) exchange.

Signals and Capabilities

The DE-15 connector carries analog RGBHV signals — three analog color channels plus separate horizontal and vertical sync. This makes it fundamentally different from the TTL digital signals carried by the earlier DE-9 connector used for CGA and EGA.

VGA-compatible signals support a wide range of resolutions and refresh rates through variable sync frequencies. The same cable and connector accommodate everything from the original VGA mode (640×480 at 60 Hz) up to QXGA (2048×1536 at 85 Hz), depending on the capabilities of the source and display devices and the quality of the cable.

Cable quality has a significant effect on signal integrity at higher resolutions. Longer runs and lower-quality cables can introduce ghosting (from impedance mismatches), color fringing (from crosstalk), and blurriness (from bandwidth limitations).

Use on CRT Equipment

Computer CRT Monitors

The DE-15 connector was the standard video input on virtually all VGA-compatible CRT monitors from the late 1980s through the end of CRT production. Multisync monitors — capable of accepting a range of horizontal and vertical sync frequencies — became the norm, supporting multiple resolutions from a single input.

High-end CRT monitors often featured multiple DE-15 inputs, or a combination of DE-15 and BNC inputs, allowing users to switch between signal sources.

CRT Televisions

Some late-model CRT televisions (particularly high-definition CRT sets from the early 2000s) included a DE-15 VGA input alongside traditional consumer A/V connections, allowing direct connection of a PC. These sets typically supported a limited set of resolutions (480p, 720p, 1080i) through the VGA input.

Professional Monitors

Professional and broadcast CRT monitors more commonly used BNC connectors for RGBHV signals rather than DE-15, as BNC provides better shielding and a true 75Ω impedance match. However, adapters and breakout cables between DE-15 and five-BNC (R, G, B, H, V) are widely available and commonly used.

Adapters

Common adapters involving the DE-15 connector include:

• DE-15 to 5×BNC — breakout cable splitting VGA into individual R, G, B, H-sync, V-sync BNC connectors for professional monitors
• DVI-I to DE-15 — passive adapter using the analog pins present on DVI-I connectors (not compatible with DVI-D)
• DE-15 to HDMI — requires an active converter (analog to digital conversion)
• DE-15 to component RCA — VGA to YPbPr transcoder, useful for connecting PCs to consumer CRT televisions

See Also

• DB-9 — 9-pin DE-9 connector used for CGA/EGA digital video
• BNC — Professional video connector, often used for RGBHV
• HDMI Type A — Digital successor to VGA on consumer displays
• RGBHV — Analog RGB signal format with separate H and V sync