excelPTZ PTZ200, Инструкция по установке и эксплуатации

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PLEASE NOTE - Using inferior cables, or installing the dome in an environment with strong
electromagnetic interference, or connecting a lot of PTZ domes to the same cable carrying the RS485 signal
will reduce the maximum transmitting distance.
3. RS485 Connection methods
METHOD 1 – DAISY CHAIN CONNECTION.
The general RS485 standard recommends a “daisy chain” connection of equipment that is to be
controlled. This means that the control cable is looped out of the one dome to the next dome and so on.
The last dome in the line is then fitted with what is known as a “termination resistor”. This has a value
of 120 .
The resistor is built in the PTZ200 domes and is activated by setting a jumper switch JP1 to ON. The
keyboard itself generally has a built-in 120 resistor. These termination resistors help make the signal
more stable and give the system better reliability so that the domes function as expected. A common
mistake installer’ s make is not making sure the 120 resistor is switched ON in the LAST dome. Also
installers often select the resistor to ON in another dome in the chain, these errors will make control of
the dome unpredictable.
A simplified Daisy chain is shown below;
This first diagram shows the cables looping in one dome and out of another;
120 120
1# 2# 3# 4# 32#
. . . . .
Standard Daisy-Chain connection for the RS485 PTZ control signal
(just the last dome only has the 120 resistor set to on, the first device is the keyboard and has the 120 built in as default)
This next diagram is a slight variation on the Daisy Chain arrangement. Again it’ s one cable going out to all
the domes but instead of the cable going into each dome then back out to the next one, a junction box is used
to “Spur-Off” to each dome. Whilst this can be done THE SPUR LENGTH (D) must be NO MORE THAN 7
meters!!!!!!!!!!!! The overall cable length between the Controller and the last dome is limited to around
300 meters in such an arrangement.