X
X
L
L
D
D
C
C
M
M
A
A
N
N
.
.
d
d
o
o
c
c
2
2
-
-
2
2
R
R
E
E
V
V
E
E
Initially following power-up, the optional open collector alarm output will provide a high impedance to
ground. When the XL-DC is tracking satellites and is controlling the local oscillator and 1 PPS output to
within specified accuracy to UTC, this output will provide a low impedance to ground. Thereafter,
whenever the XL-DC outputs are not within specifications, this output will provide a high impedance to
ground.
2-3 SPECIAL CONSIDERATIONS FOR EXTERNAL OSCILLATOR CONTROL OPTION
Interconnection between the XL-DC and the external oscillator to be controlled must be planned
carefully. Of particular importance is the elimination of ground loops made by the connection of power
supply returns, DAC control voltage return and the signal ground shield. Some types of oscillators are
particularly susceptable to noise in these loops which can cause missing pulses to occur at the XL-DC
External Oscillator input signal conditioning circuits.
The recommended connection method is as follows:
1)
Provide a single ground path between the XL-DC and the External Oscillator.
2)
Let that single ground provide the DAC tuning voltage return.
3)
Transformer couple the External Oscillator signal into the XL-DC to break the
coaxial ground connection, thereby eliminating that potential ground loop.
Following these guidelines will provide reliable operation with a wide variety of oscillators.
2-4 RACK MOUNTING
The XL-DC mounts in a standard 19 inch rack system using the rack mounting brackets provided.
These brackets may be attached to the sides of the cabinet. First remove the flat head screws from
each side of the instrument. Place the screws supplied with the brackets (part number 241-008-005, 8-
32x5/8) through the countersunk holes in the brackets then into the clock and tighten. The unit may
now be mounted in a 1-3/4 inch opening in any EIA Standard 19 inch rack system. The optional Rack
Mounting Slide Kit includes installation instructions.
Do not block ventilation openings. Doing so may cause the unit to exceed the maximum operating
temperature of +50
û
C.
Summary of Contents for 151-600
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