Murata Electronics North America ZN241 Manuel D’Utilisation

Figure 1 --  ZN241/Hypercom System Block Diagram 
 

 

 
 

Frequency Selection 
 
The ZMN2400 is not frequency agile during run-time, but it can select an 
unoccupied portion of the spectrum at startup from among the choices 
programmed into the Channel Mask.  We believe the most likely source of 
interference would be from nearby 802.11b access points, which typically 
default to one of the following three channels: 
 
 

 

   

1 

      

 

 

 

2412 

      2401-2423 
  

  

6 

      

 

 

 

2437 

      2426-2448 
  11 

      

 

 

 

2462 

      2451-2473 
 
ZigBee defines channel centers from 2405 to 2480 with 5 MHz spacing.  
Our strategy is to balance between keeping the number of possible 
channels as few as possible (to minimize variation from power-up to 
power-up) and to avoid possible 802.11b interferers.  With this in mind, 
we can select three channels, one at 2480, completely above the three most 
common 802.11b channels, and two at the nulls between channels at 2425 
and 2480: 
 
 

 

 

 

    15   

 

 

 

    2425 

 

     2422.5-2427.5 
 

 

    20   

 

 

 

    2450 

 

     2447.5-2452.5 
 

 

    26   

 

 

 

    2480 

 

     2477.5-2482.5 
 
The channels in the 2.4 GHz band span from 11 to 26.  Only these 
channels are supported by the ZMN2400.