Clear-Com PS-704 - Manual (Page 20)

P S - 7 0 4 F O U R - C H A N N E L P O W E R S U P P L Y 2 - 6
CROSSTALK CONSIDERATIONS
When multiple channels are fed to remote stations, the amount of crosstalk
between channels is proportional to the DC resistance of the ground return
path back to the channel terminations. To minimize this crosstalk between
channels when running more than one channel in a multi-pair cable, keep the
DC resistance of the ground return as low as possible. Ideally, this should be
less than 2
Ω. This can be achieved as follows:
• Keep cable runs under 500 ft. (152.5 m).
• Use a cable whose common shield has a low DC resistance.
• Connect unused cable wires of a multi-pair cable to the pin #1 shield.
If shielded multi-pair cables are used to connect multiple channels between
the PS-704 and remote stations, the cables should be wired to maximize the
number of ground connectors to minimize crosstalk. In the following cable
wiring diagram, note that it is not necessary to run redundant power
connectors on each channel to the remote station. The spare wires which
would normally conduct power are instead used to augment the drain wire
ground connection.
Figure 2-5: PS-704 to 4-Channel Remote Station
Note: All multi-pair cables must have individually shielded pairs.
Clear-Com recommends the Belden 1800 series of multi-pair cables. They
offer a common shield with a low DC resistance in addition to individual
shields on each pair.
Typical system performance for a Clear-Com system is contingent on the use
of Clear-Com or Clear-Com approved compatible headsets. Use of headsets
other than these can induce crosstalk into a multi-channel system through the
headset cable. Clear-Com does not recommend the use of headset extension
2
3
1
PS-704
Power
Supply
A
B
C
D
2
3
1
2
3
1
2
3
1
2
3
1
4-Channel
Remote
Station
A
B
C
D
2
3
1
2
3
1
2
3
1
P ower
C h. A Audio
C h. D Audio
C h. B Audio
C h. C Audio
G nd*
G nd*
G nd*
* = S pare W ire used for G nd
Drain wire G nd
C h. D Audio
G nd*
C h. C Audio
C h. B Audio
G nd*
G nd*
C h. A Audio
P ower
Drain wire G nd
** = If the s hields from individual
pairs are brought out s eparately,
they mus t als o be connected to
P in 1.
S hield**
S hield**
S hield**
S hield**
S hield**
S hield**