I checked the product data sheet for the 1400, here is what they said:

The concept of mobile networks is significant not only for service providers looking to offer seamless network access, but also for individual organizations such as municipal public safety units. In many instances, the technology exists to create the zones that provide the mobile network, but the challenge lies in bringing the network to these zones. The Cisco Aironet 1400 Series Wireless Bridge provides a cost-effective solution to this application. The wireless bridge can connect to the network that contains the 2.4 GHz access points or bridges that are providing wireless zone coverage, and also provide the backhaul link to the high-speed network (Figure 2). Whether these zones are 802.11 hot spots at cafes and restaurants or bridged 802.11b cells for mobile networks, the Cisco Aironet 1400 Series Wireless Bridge provides a non-interfering and higher speed distribution service.

Here is the data sheet for the 1400 and they are only 5 GHz. I think that document is wrong

http://www.cisco.com/en/US/prod/collateral/wireless/ps5679/ps5279/ps5285/product_data_sheet09186a008018495c.html

The extract this paragraph from the same sources below:

http://www.cisco.com/en/US/prod/collateral/wireless/ps5679/ps5279/ps5285/product_data_sheet09186a008018495c.html

in the "Mobile Networks and Wireless Bridges" section.

Can it still works with the 2.4 GHz?

As George had said, the 1400 is a 5Ghz AP only.  From the link you posted, look at Table 2.

Steve

I am really appreciated your helps Stephen and George. This information is help alot.

yea, it saves you problems on the back end.

Keep in mind, Cisco axed both of these...