NF9 AF access unit

 AF access unit

          NF9 is a programmable low frequency access unit with universal telephone interface (UTI). NF9 unit consists of the following blocks:
 - UTI - universal telephone unit; 2-w or 4-w interface; 
 - AF1 - multipurpose AF interface; 2x 4-w interface; 
 - AF2 - multipurpose AF interface or teleprotection interface; 4-w interface; 
 - AF1 line interface, applicable only in case of external mode of operation; 4-w interface.


          Universal telephone interface is entirely programmable. Basic function of NF9 unit is multipurpose use of TC channel. Multipurpose use refers to the simultaneous use of TC channel for transmission of various types of data:
 -  speech with corresponding signalization,
 -  narrow band modems signals,
 -  signals of various terminal equipment within 4 kHz AF band,
 -  signals of equipment for transmitting teleprotection commands.

          It plays the role of an interface between the speech and the signalling sub-channel on the one side and various types of telephone network elements on the other: 
- inductor telephone set with local battery, with or without dial - LB;
- automatic telephone set with central battery with or without dial - CB;
- automatic telephone set with central battery and dial - ATA;
- private automatic exchange; 2-wire subscriber line (local or remote (LLE) client connection) - PA(B)X; 2-w;
- private automatic (branch) exchange; 4-wire connection with E&M signalization (“trunk” connection towards PA(B)X or remote client connection (LLE) on the exchange side) - PA(B)X; 4-w, E&M.

          Two universal 4-w interfaces AF1 and AF2 are available on the NF9 unit. They are provided for connecting various devices, operating within AF range and using PLC channels as telecommunication media. Each of the interfaces consists of input and output with factory installed impedance of 600 Ohm. Value of input and output impedance can be set at 300 Ohm, 600 Ohm and high Z. Operating frequency range of the devices, connected to AF1 and AF2 interfaces should be within 300 – 3720 Hz band. All signals within mentioned band are transparently transmitted through PLC channel.

          NF9 is used as AF access unit of ET9 equipment – integrated mode of operation or as independent device – external mode of operation.

          Integrated mode of operation
          NF9 unit represents AF access unit of ET9 equipment.
          In case of integrated mode of operation mapping of user interfaces AF1, AF2 and UTI into not more than two PLC channels of ET9 equipment is enabled.

          External mode of operation
          An independent NF9 device consists of one or more NF9 units with UCR housing, PS power supply part and CMS supervision unit. AF1 interface operates as line interface. All signals on NF9 access unit 4-w AF1 interface are analog and within frequency range from 300 to 3720 Hz; also pulse signalization and ringing voltage (transmission of both appropriately transformed signals is executed in the FSK signaling channel). 

          NF9 unit in external mode of operation enables operation of the following user interfaces:  
 - 1x analog speech interface; FXS, FXO, 4-w E&M;
 - 1x 4-wire AF2 AF interface with transit filters.

          Also, when using this mode of operation of NF9 unit, AF1 interface is used as line interface, therefore
connecting of other devices to it is not possible.