This section by Andreas Koch.

- Atari Paddles (usually a pair of Paddles);
- Telegames Paddles (available as a) a single paddle and b) a pair 
  of paddles);
- Reston Paddles (available as a) a single paddle and b) a pair 
  of paddles);
- and many others...

Note: Both single and duo (pair) paddles are compatible to each other,
using only one port-connector (only one joystick port). Thus, with a pair 
of paddles you can connect up to 4 paddles (2 pairs) to the XL/XE models
and up to 8 paddles (4 pairs) to the Atari 400/800 models.