4
Functional Block Diagram of
XRD-8050 and XRD-8050/RK
Theory of Operation
The FIBERLINK XRD-8050 is user-configurable to one of two modes, MASTER
or LOCAL, and the block diagram below shows the signal flow in either of these
configurations. As will be noted from the diagram, the unit consists of two
optical transmitters and two optical receivers contained within the same housing.
Depending on the setting of an internal MASTER/LOCAL switch, the intercon-
nections between the transmitters and receivers are varied to properly input,
output and/or repeat the data signals as required.
In addition, an anti-streaming circuit is provided to monitor the RTS port. If any
traffic signal controller connected to the XRD-8050 reverts to a streaming
condition, the pre-set time-out of the anti-streaming circuit will be exceeded and
all further data from the faulty controller will be blocked thereby preventing
system lock-up.
A rechargeable internal battery is provided in the stand-alone version of the
XRD-8050. In typical traffic signal network communications, this battery can
provide up to 12 hours of operation during the loss of prime power.
13
OVERALL SYSTEM CHECKOUT AND TROUBLE-
SHOOTING TECHNIQUES
A. Check Transmitter (or transmitting section of a transceiver)
1. Is the operating power (DC, AC, Voltages) correct?
2. Are the pins being used on the connector or terminal block correct?
.
3. Is the correct signal level present at the transmitter input?
4. If the unit is a digital transmitter, does the transmitting LED glow
dimly when a signal is applied? Note that this is only true at an
operating wavelength of 850nm. Light at 1300nm is totally invisible. *
5. If the unit is an analog or video transmitter (at 850nm) is there a
continuous dim glow from the transmitting LED? *
6. Is the optical connector on the transmitter clear of any obstruction or
minute dirt particles?
7. Does it matter that signal ground and power ground of many systems
are common?
8. Does the fact that signal ground, power ground and the housing are
common cause a short-circuit anywhere in the system?
* The above visual check should only be attempted with LED type emitters.
Occasionally, during the installation of a fiber optic transmission system,
difficulties arise that are the result of factors beyond the control of the installer.
It is to simplify the task of the installer that the following general checkout
procedure is included.
US Government regulations require that all equipment using Laser Diodes be
clearly identified with appropriate warning labels. Be sure to heed these labels.
NEVER LOOK DIRECTLY AT AN OPERATING
LASER
DIODE, REGARDLESS OF THE
OPERATING WAVELENGTH
