A number of considerations need to be made when designing a cctv system. Power requirements, distance, cabling to name a few...

Single Versus Multiple Port
If you are running a single camera, or maybe 2 camera security system, it is probably more cost effective to purchase a single power supply adapter for each camera. Up to 4 single camera supplies off of a power strip may work when you are designing this type of system, but neatness may count for something as well. A single power supply box offers an effective, attractive solution for multiple camera power.

DC or AC CCTV Power
CCTV and security systems have until the last 10 years been primarily 24VAC. Advent of smaller, more compact and covert cameras has resulted in an increasing number of 12 volt DC installations. Both are lightly regulated (low voltage) for construction allowing flexible securty and surveillance installations, and each has its advantages.

12VDC requires a smaller footprint for a camera because it does not require a built in rectifier. though originally adopted for covert camera applications, it became popular for larger C/CS cameras as it lessened the manufacturing costs. 12vDC is NOT good for long cable runs however, and some 12V DC power supply boxes are more costly than their 24V AC counterparts. Also, for some time the 12V DC powered camera was shunned by many professionals because it was hard to get "in phase" when installed in a Multiplexed video system. Current Digital video recording has all but eliminated this problem.

24VAC Power supplies are often simple transformers distributed into multiple ports, or used singly. Advantage is cost in multiple port systems because of reduced components. 24VAC power performs better over long runs with less need for heavy gauged wire runs. Most, but not all outdoor housings which have blowers and heater, require 24VAC. The power consumption is better handled with 24VAC as well.

Often, mixed systems exist where both types of cameras are used. Newer12V DC camera addtions to established 24VAC systems can be accomodated with the use of power converters. These are simple devices which regulate a 24VAC voltage to 12V DC. Sometimes the 24VAC to 12VDC power converter is used when sending power over a distance to a 12VDC camera. If you need to use these power adapters, allow overhead on the current rating. IE: 400ma required for a 12V camera could use an 800ma ac to dc converter. This would ensure the camera does not overload the converter avoiding potential converter failure.