USB (Universal Serial Bus) Overview
- USB stands for Universal Serial Bus, the standard connection type for peripherals
like keyboards, mice, and other devices.
- USB has evolved through multiple versions, each improving speed and functionality.
USB Versions and Specifications
- USB 1.1:
- Operated at two speeds: Low Speed (1.5 Mbps) with a maximum cable length of
3 meters.
- Full Speed (12 Mbps) with a maximum cable length of 5
meters.
- USB 2.0:
- Maximum speed of 480 Mbps over a 5-meter cable.
- USB 3.0 (SuperSpeed):
- Maximum speed of 5 Gbps over a 3-meter cable.
- USB 3.1:
- Maximum speed of 10 Gbps.
- USB 3.2:
- Maximum speed of 20 Gbps.
- USB specifications do not define exact cable lengths, but the listed lengths are typical maximums
for maintaining throughput.
USB Connectors
- USB 1.1 and 2.0 Connectors:
- Standard A Plug: Common rectangular connector still used today.
- Standard B Plug: Square-shaped, used for printers and external devices.
- Mini B Plug and Micro B Plug: Smaller connectors for
mobile devices.
- USB 3.0 Connectors:
- Standard A Plug: Same form factor as USB 2.0 but often blue for
identification.
- Standard B Plug: Taller than USB 2.0 version.
- Micro B Plug: Different form factor from USB 2.0 Micro B.
- USB-C:
- Standardized connector designed to replace older USB types.
- Reversible orientation (no "right-side up").
- Supports multiple signal types (data, power, video) but does not define the signal itself.
- Similar in size to Micro B but with a symmetrical design.
Serial Connections (RS-232)
- Before USB, serial cables were used for peripherals like modems, keyboards, and
mice.
- RS-232 (Recommended Standard 232):
- Standard for serial communication since 1969.
- Common connectors: DB9 (DE9) and DB25.
- DB9: 9-pin connector (technically DE9 but commonly called DB9).
- DB25: 25-pin connector.
- Modern uses:
- Connecting to legacy equipment like switches, routers, or firewalls via console
ports.
- Console ports may use RJ45, DB9, or USB
connectors.
- Adapters are often needed to connect modern USB ports to older DB9 or RJ45 console ports.
Thunderbolt Overview
- Thunderbolt is a high-speed serial connection combining data and power in a single
cable.
- Supports daisy-chaining devices (e.g., computer → monitor → monitor → storage).
Thunderbolt Versions and Specifications
- Thunderbolt 1:
- Used Mini DisplayPort connector.
- Two channels of 10 Gbps each (total 20 Gbps).
- Thunderbolt 2:
- Aggregated throughput of 20 Gbps.
- Still used Mini DisplayPort connector.
- Thunderbolt 3:
- Uses USB-C connector.
- Aggregated throughput of 40 Gbps.
- Maximum cable length: 3 meters (copper) or 60 meters
(optical).
- Thunderbolt 4:
- Aggregated throughput of 40 Gbps.
- Supports dual 4K displays.
- Increased bandwidth to PCI Express bus for faster data transfer.