1. Small Business Systems (key systems)
Don’t have the same number of facilities as a PABX.
Most obvious difference: all exchange lines and extensions appear on each
handset.
To get outside like user selects a free line and dials number.
Buttons are usually illuminated.
Single button use.
Heart of a SBS need powerpoint and access to the cable distributor.
Similar to a PABX, but on a smaller scale.

2. Small Business Systems (key systems)

3. Automatic call distributor (ACD)
Software option.
People who are calling wait in a cue until an operator is
available to take their call.