Comdial DXP Plus Series, Руководство пользователя

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Understanding The DXOPT-SYN Synchronization Card
The DXOPT–SYN card uses a reference timing frequency of 8 KHz that it derives from the 1.544 MHz frequency
supplied to the T1/PRI board by the central office (CO) or other external source. By referencing this 8 KHz with
8 KHz timing derived internally, the master 16.384 MHz voltage-controlled oscillator (VCO) can be
synchronized. The transmit clock (1.544 MHz) is derived from the 16.384 MHz frequency on the T1/PRI board. If
the 1.544 MHz received frequency is incorrect (not within a 200 Hz tolerance), the system may loose
synchronization with the CO or other external source. The DXOPT–SYN card reports this condition by turning on
the appropriate alarms on the T1/PRI board and DXOPT–SYN card. A loss of clock synchronization causes frame
slips that result in data communications errors.
The DXOPT–SYN card allows two timing references ( primary and secondary) to be selected. You can select
either automatic or manual (for maintenance mode). In the automatic mode, a loss of primary timing causes the
system to switch to the secondary timing reference. If both the primary and secondary timing references are lost,
the VCO oscillator on the DXOPT–SYN card is defaulted to the fixed 16.384 MHz oscillator on the services
board. This results in the loss of clock synchronization.
Installing And Programming The DXPRI Card IMI89–255
Understanding The DXOPT-SYN Synchronization Card – 3