NET_13.TXT
                        BACKBONE TRUNK WITH REGENERATOR
                        -------------------------------

A  variation  of the  cross-band  full-duplex  configuration  would be to add a
full-duplex regenerator,  either  embedded within a trunk,  or at a junction of
the backbone trunk.  A cross-band full-duplex regenerator is  fairly economical
to install and on a less then fully loaded  network  operates  reasonably well.
There  is  a  performance  penalty  though  since it doesn't have the same high
throughput as a full duplex-link.    However in terms of a cost vs. performance
trade-off, it's worth considering at selected sites.

-------------------------------------------------------------------------------
         FULL DUPLEX CROSS BAND BACKBONE TRUNK WITH DUPLEX REGENERATOR

NODE A                 NODE B             NODE  C            NODE E
======                 ======             (REGEN)            ======
147.5 TX ------------> 147.5  RX          =======
446.1 RX <------------ 446.1  TX
                       147.52 RX <------- 147.52 TX -------> 147.52 RX
                       446.2  TX -------> 446.2  RX <------- 446.2  TX
                                                             147.54 RX <----
                                      |               |      446.1  TX ---->
                                      |    NODE F     |
                                      |    ======     |
                                      `-> 147.52 RX   |
                                          446.2  TX >-'
                                      .-> 147.56 RX
                                      |   446.3  TX >-.
                                      |               |
                                      |               |
                                      |               |


                                  Figure 13-1
-------------------------------------------------------------------------------

There  are other possible frequency/equipment configurations that are workable.
But  the  full-duplex  backbone  approach offers  advantages of flexibility and
efficiency.  It won't  become  obsolete in the foreseeable future.  While  more
expensive than a simplex backbone trunk,  full-duplex is economical in terms of
yielding  increased  throughput  even  at 1200 baud.    Indeed, its performance
is comparable to that of a simplex 4800 to 9600 baud system.

Full-duplex is flexible  from  the viewpoint that it can be upgraded on a link,
rather than a system basis as assets  become available.    For instance, if the
basic trunk is initially installed as a 1200 baud  system, individual links can
be upgraded to higher data rates on an independent schedule.

Obsolescence is forestalled by the mechanics of the configuration.    Assume in
five  years chronic network overload will have set in.   If RF path engineering
was  done  with the view of  eventually phasing in microwave, link segments can
be installed as funds and equipment become available.   Surplus equipment could
either be held on site for backup use or relocated/sold as necessary.

For  this  system configuration concept to be satisfactory,  it's important the
network  is engineered on an intra and inter-state basis.  The primary emphasis
would  be  directed  to  building  a  robust backbone trunking system served by
isolated  frequency  LANS  supporting both 1200 and 9600 baud access nodes.  It
would  be a  good policy  to include state and county emergency service offices
into  the project planning so the network's digital support capability could be
utilized  by  them in case of emergency.   In the same light, local governments
may be able to provide site support, and possibly, help with project funding.