American Telecom AM64/128A - Manual (Page 33)

AM64/128A User Manual Menu Operation - Configuration Menu
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5.7 Configuration Menu
This menu contains the items that are used in the initial configuration of the BBM. Once set up they are
usually left unchanged for normal BBM operation. All of the configuration parameters are stored in non-
volatile memory and are restored each time the BBM is powered up.
The items in this menu are as follows:
(1) Master - Slave
(2) Line rate
(3) X.21 loop control (Not available for certain interfaces)
(4) Synchronisation type
(5) 64k mode
(6) Transmit power level
(7) Menu lock
5.7.1 Master - Slave
When two BBM’s are connected together to form a link, one must always be a master while the other has
to be set as a slave. The transmission signal is different for master and slave, so line synchronisation will
never be achieved if two like types (e.g. Master-Master) are connected together. Normally it makes no
difference which BBM is which, but there are a few extra facilities included in the master mode.
These are:
(1) Selection of the user data rate, (see section 5.5).
(2) External bit/byte timing synchronisation, (see section 5.7.4).
(3) Provision of 64k mode, (see section 5.7.5).
(4) Extra error monitoring facilities, (see section 5.4.6).
The default setting is to slave mode : C > Slave Mode
Pressing SELECT gives : C > Master Mode
5.7.2 Line Rate
The line rate is the basic bit rate of the transmission between the two BBM ‘s. This must be set locally to
the BBM via the front panel in both Master and Slave BBM’s and cannot be downloaded from the Master
unit. There are two settings
High Rate and Double Rate. The high rate gives a better range, but lower
user data rates.
The high rate is shown as: C > 64K Rate
Pressing SELECT gives the double rate, shown as: C > 128K Rate
High rate is 71.1 kbps, and all user data rates (except 128k) are allowed. The maximum operating distance
depends upon the cable dimensions, an example is 5km when used with 0.4mm cable, (corresponding to
50dB attenuation).
Double rate is 142.2 kbps, and only user data rate 128 kbps is allowed. The distance on 0.4mm cable is
to 4km, (40dB attenuation).