3010-dda.ib.rev1.doc
Page 6 of 10
05/07/2006
Technical Description
The input circuit of the DDA-3010 consists of an adaptive cable equaliser IC, which automatically adapts to equalise
any cable length from zero metres to lengths that attenuate the signal by 40 dB at 200 MHz. This corresponds to
300 metres of Belden 8281 cable. A carrier detect and output mute circuit is used to mute the output when no signal
is present.
The DDA-3010 also features an OUTPUT MONITOR point on the front panel. The output monitor is an isolated
copy of the signal present at the rear panel outputs.
The output of the input stage is coupled to a reclocking circuit, which then feeds cable driver circuits to provide the
six isolated in phase outputs from the DDA-3010.
The input cable equaliser and reclocking circuits incorporate carrier detection circuits to mute the output when no
signal is applied to the unit. The carrier detect signal and lock signal of the reclocker are used to energise relay, RL1
via a transistor, Q1, when locked carrier is present. A second relay, RL2, de-energises on loss of power to give a
separate alarm for loss of power. The relay contacts are connected to SK10 on the rear panel to give a failure alarm
in the form of a make (or break) to ground on failure as set by a links LK1 and LK2, respectively, on the circuit
board.
The dual AC inputs are rectified and then regulated by a switch mode regulator circuit to provide the +5V operating
voltage for the unit.
+5Vdc is fed to pin 32a of the rear Euro-connector via a polyfuse, F5. The +5V is to provide power for a signal
bypass relay rear assembly. The polyfuse protects the +5V power rail by going high impedance should pin 32a be
shorted to ground. This protects against the accidental insertion of the DDA-3010 in anything other than its standard
rear assembly.
