Some cameras have a built-in microphone with an audio output socket that can be connected to your Mac through an audio input device. Alternatively, you can use separate microphones. Note that some microphones output a mic-level signal; others output a line-level signal, which is stronger. Similarly, some audio input devices require a mic-level signal while others (such as the built-in inputs in the Mac) require a line-level signal. Generally it is best to use a line-level signal, because the cable length between the microphone and the audio input device may be quite long, and line-level signals are less prone to noise and interference.
Line level microphones contain a pre-amp which requires power, in which case you will need a 12V power supply and, ideally, a combined power-and-audio cable to connect the microphone. Some cables have two power connectors, in which case you can power a microphone and a camera with the same cable.
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Choosing a system
Types of camera
Progressive scan
System demands
Example systems
Budget
Home or small business
Professional
Network cameras
Choosing network cameras
Network hardware
Ethernet cabling
Local networks
Setting up network cameras
Setting up wireless cameras
Network camera notes
Analogue cameras
Analogue cabling
Quad processors
Choosing input hardware
Network video servers
PCI input cards
Firewire inputs
USB inputs
Audio input
Microphones
Remote monitoring
Internet connection
Seting up your Mac
Setting up your router