Optelecom 9525A User manual

Optelecom 9000 Series
Installation and Operation Manual
Model 9525A
Dual Optics RS232, RS422, or RS485
Drop and Insert Modem
UM50235, Manual 9525A, Rev. D

3
Table of Contents
Section Page
Safety Instructions 4
Instrucciones de Seguridad 5
Sicherheitsanleitungen 6
Consignes de Sécurité 7
External Wiring Information 8
1 - INTRODUCTION 9
1.1 General description 9
1.2 Physical Specification 10
1.3 Environmental Specification 10
1.4 Functional Specifications 11
2 - INSTALLATION 13
2.1 System Architecture 13
2.2 Modes of Operation 15
2.3 Operational Features and Considerations 18
2.4 Set-Up Procedures 21
2.5 Mounting 24
2.6 Optical Cabling 24
2.7 Electrical Cabling 25
2.8 POWER WIRING 26
3 - OPERATION 27
3.1 Turn on Procedure 27
3.2 Indicator Light Interpretation 27
3.3 BERT Test 28
3.4 Ring Integrity Test (Master Fault Tolerant Mode) 28

4
Safety Instructions
The optical devices used in this equipment are Hazard Level 1M. As required by IEC60825-1, the installer is responsible for insuring that the label
depicted below is present in the restricted locations where this equipment is installed.
This assembly contains parts sensitive to damage by electrostatic discharge (ESD). Use ESD precautionary procedures when
touching, removing, or inserting parts or assemblies.
The DC power input connector serves as a service disconnect for this module. This module is intended for installation in
locations that provide suitable access to the DC power input connector.
The chassis into which this unit is installed must be housed in a properly rated NEMA enclosure.
When this unit is operated in extremely elevated temperature conditions, it is possible for internal and external metal
surfaces to become extremely hot. Care should be taken to insure this unit is installed in a restricted area where only
properly trained service personnel have access to the unit.
The safety information contained in this section, and on other pages of this manual, must be observed whenever this unit is operated,
serviced, or repaired. Failure to comply with any precaution, warning, or instruction noted in the manual is in violation of the standards of
design, manufacture, and intended use of the unit. TKH Security Solutions USA assumes no liability for the customer’s failure to comply
with any of these safety requirements.
SA-1
LASER RADIATION
DO NOT VIEW DIRECTLY WITH OPTICAL INSTRUMENTS (MAGNIFIERS)
CLASS 1M LASER PRODUCT
WARNING: Viewing the laser output with certain optical instruments (for example: eye loupes, magnifiers and
microscopes) within a distance of 100 mm may pose an eye hazard.
CAUTION:
DISCONNECTED OPTICAL CONNECTORS MAY EMIT OPTICAL ENERGY.
DO NOT VIEW BEAM WITH OPTICAL INSTRUMENTS
This product contains Class 1M lasers or LEDs.
• Class 1M laser product according to IEC60825-1:1993+A1+A2
• CAUTION: Use of controls or adjustments or procedures other than those specified herein may result in hazardous radiation exposure.
• Precautions should be taken to prevent exposure to optical radiation when the unit is removed from its enclosure or when fiber is
disconnected from the unit.
•Laser radiation may be present on a fiber connection to this unit even when the power has been removed from the unit.
•This unit is intended for installation in locations where only trained service personnel have access to the fiber connections.
•The locations of all optical connections are listed in the Connection Locations and Function section of this manual.
•Optical outputs and wavelengths are listed in the Specifications section of this manual.
Hazard Level 1M
The border shall be black and the
background shall be yellow

5
Instrucciones de Seguridad
Los dispositivos ópticos usados en este equipo son de Nivel de Riesgo 1M. Según lo exige la norma IEC60825-1, el instalador es responsable de
asegurar que la etiqueta descrita a continuación esté presente en las áreas restringidas donde se instale este equipo.
Este ensamblaje contiene piezas sensibles al daño por descargas electrostáticas (ESD, por sus siglas en inglés). Use
procedimientos para prevenir las descargas electrostáticas al tocar, desmontar o insertar piezas o ensamblajes.
El conector de entrade de energía de CC sirve como desconector de servicio para este módulo. Este modulo está destinodo a
instalarse en ubicaciones que ofrecen acceso adecuado al conector de entrade de energía de CC.
El chasis en el cual está instalada esta unidad debe estar dentro de un alojamiento debidamente calificado por NEMA.
Cuando se opera esta unidad en condiciones de temperatura sumamente elevada, es posible que las superficies internas y
externas de metal se pongan extremadamente calientes. Debe tenerse cuidado para asegurar que esta unidad se instale en
un área restringida donde sólo tenga acceso a la unidad el personal de servicio debidamente capacitado.
Debe observarse la información de seguridad contenida en esta sección, y en otras páginas de este manual siempre que se opere, dé
servicio o repare esta unidad. Si no se cumple con alguna precaución, advertencia o instrucción indicada en este manual se infringen los
estándares de diseño, fabricación y el uso destinado a la unidad. TKH Security Solutions USA no asume ninguna responsabilidad si el cliente
no cumple con alguno de estos reequisitos de seguridad.
SA-1
SA-1
RADIACIÓN LÁSER
NO VER DIRECTAMENTE CON INSTRUMENTOS ÓPTICOS (DE AUMENTO)
PRODUCTO LÁSER CLASE 1M
¡PRECAUCION¡: Mirar la salida del laser con ciertos instrumentos ópticos (ej., lentes, anteojos, lupas de aumento,
microscopios, etc.) dentro de una distancia de 100 mm podría ocasionar lesions permanents en los ojos.
PRECAUCIÓN:
LOS CONECTORES ÓPTICOS DESCONECTADOS PUEDEN AMITIR ENERGĺA ÓPTICA
NO VER EL HAZ CON INSTRUMENTOS ÓPTICOS (DE AUMENTO)
Este producto contiene rayos láser o diodos emisores de luz Clase 1M.
• Producto láser Clase 1M conforme a la norma IEC60825-1: 1993+A1+A2
•PRECAUCIÓN: El uso de los controles, ajustes o procedimientos, aparte de los aquí especificados, pueden ocasionar exposición peligrosa a la
radiación.
•Deben tomarse precauciones para evitar la exposición a la radiación óptica cuando se saque la unidad de su alojamiento, o cuando se
desconecte la fibra de la unidad
• Puede haber radiación laser en una conexión de fibra a esta unidad aun cuando se haya eliminado la corriente de la unidad.
•Este equipo está destinado a instalarse en lugares donde sólo el personal de servicio debidamente entrenado tenga acceso a las conexiones
de fibra.
•La ubicación de todas las conexiones ópticas se enumeran en la sección Ubicación de los conectores y funciones de este manual.
•Las salidas ópticas y longitudes de onda aparecen en la sección Especificaciones de este manual.
Nivel de Riesgo 1M
El bordo debe ser negro y
el fondo debe ser amarillo

6
Sicherheitsanleitungen
Die optischen Vorrichtungen in diesem Gerät haben Gefahrenstufe 1M. Wie vorgeschrieben durch IEC60825-1 ist der Installateur dafür verantwortlich,
sicherzustellen, dass die unten abgebildeten Schilder an den Orten mit eingeschränktem Zugang, an denen dieses Gerät aufgestellt ist, vorhanden sind.
Diese Baugruppe enthält Teile, die durch elektrostatische Entladungen (ESD) beschädigt werden können. Vorsichtsmaβnahmen
zum Schutz vor elektrostatischer Entladung treffen, wenn Teile oder Baugruppen berührt, ausgebaut oder eingefügt werden.
Der Gleichstrom-Eingangssteckverbinder dient als Unterbrechung der Stromversorgung für dieses Modul. Dieses Modul ist für
den Einbau an Orten vorgesehen, an denen geeigneter Zugang zu einem Gleichstrom-Steckverbinder vorhanden ist.
Das Gestell, in dem diese Einheit eingebaut ist, muss in einem entsprechend klassifizierten NEMA-Schutzgehäuse untergebracht
sein.
Wenn diese Einheit bei besonders hohen Temperaturen betrieben wird, können interne und externe Metallflächen extrem
heiβwerden. Es muss darauf geachtet werden, dass diese Einheit in einem Bereich mit eingeschränktem Zugang aufgestellt
wird, damit nur geschultes Wartungspersonal Zugang zur Einheit hat.
Die in diesem abschnitt und auf anderen seiten dieses Handbuchs enthaltenen Sicherheitsinformationen müssen befolgt werden, wenn
diese einheit betrieben, gewartet oder repariert wird. Falls Vorsichtsmassnahmen, Warnungen oder Anweisungen in diesem Handbuch
nicht befolgt werden, verstösst dies gegen die Konstruktions, und Herstellungsstandards und erfolgt im gegensatz zum vorgesehenen
Verwendungszweck dieser einheit. TKH Security Solutions USA übernimmt keine Haftung für das Verabsäumnis des Kunden, diese
Sicherheitsanforderungen einzuhalten.
SA-1
LASER-STRAHLUNG
NICHT DIREKT MIT OPTISCHEN INSTRUMENTEN (LUPEN) ANSEHEN
LASER-PRODUKT DER KLASSE 1M
WARNUNG: Betrachtung des Laserlichtausgangs mit bestimmten optischen Instrumenten(zumBeispiel, Augenlupe-
Vergrößerungsgläser und Mikroskope) innerhalb einer Entfernung von 100 mm kann eine Augengefahr darstellen.
VORSICHT:
ABGEKLEMMTE OPTISCHE STECKVERBINDER KÖNNEN OPTISCHE ENERGIE FREI SETZEN
NICHT MIT OPTISCHEN INSTRUMENTEN (LUPEN) IN DEN STRAHL BLICKEN.
Dieses Produkt enthält Laser oder LEDs der Klasse 1M.
• Laserprodukt der Klasse 1M gemäß IEC60825-1:1993+a1+A2
• VORSICHT: Wenn die Bedienungselemente anders als hier beschrieben bzw. andere Einstellungen verwendet werden, kann es zu
schädlicher Strahlenaussetzung kommen.
•Es müssen Vorsichtsmaßnahmen getroffen werden, um Aussetzung an optischer Strahlung zu vermeiden, wenn die Einheit aus dem Gehäuse
genommen oder die Faseroptik von der Einheit getrennt wird.
• In einer Faseroptik-Verbindung dieser Einheit kan auch dann Laserstrahlung vorhanden sein, wenn die Stromversorgung zur Einheit
abgeschaltet wurde.
•Diese Einheit ist zum Einbau an Orten vorgesehen, an denen nur geschultes Personal Zugang zu den Faseroptik-Verbindungen hat.
•Die Lage aller optischen Verbindungen ist im Abschnitt über die Lage von Anschlüssen und Funktionsweise dieses Handbuchs zu finden.
•Optsiche Ausgänge und Wellenlängen sind im Abschnitt mit den technischen Daten dieses Handbuchs zu finden.
Gefahrenstufe 1M
Schwarzer Rand und
gelber Hintergrund

7
Consignes de Sécurité
Les appareils optiques utilisés dans cet équipement correspondent à un niveau de danger 1M. Comme exigé par la norme IEC60825-1, il incombe à
l’installateur de s’assurer que l’étiquette ci-dessous est présente aux endroits d’accès limité où cet équipement est installé.
Cet ensemble contient des pièces sensibles aux décharges électrostatiques (ESD). Prendre les précautions relatives aux ESD
avant de toucher, retirer ou insérer des pièces ou des ensembles.
Le connecteur d’entrée d’alimentation c.c. sert de sectionneur de maintenance pour ce module. Ce module est prévu pour
une installation à des endroits donnant raisonnablement accès au connecteur d’ entrée d’alimentation c.c.
Le châssis dans lequel est installé cet appareil doit être place dans une enceinte NEMA conforme aux spécifications nominales.
Lorsque cet appareil fonctionne à une température ambiante extrêmement élevée, il est possible que les surfaces métalliques
internes et externes deviennent extrêmement chaudes. S’assurer que cet appareil est installé dans une zone dont l’accès est
limité à un personnel de maintenance correctement formé.
Les consignes de sécurité contenues dans cette section et dans le reste de ce manuel doivent être respectées a chaque fois que cet appareil
est utilisé ou fait l’objêt d’une maintenance ou d’une réparation. Le non-respect d’une précaution, d’un avertissement ou d’une instruction
figurant dans ce manuel est une violation des normes de conception, fabrication et indication d’usage de l’appareil. TKH Security Solutions
USA n’est pas responsable du non-respect de ces consignes de sécurite par le client.
SA-1
RAYONNEMENT LASER
NE PAS REGARDER DIRECTEMENT AVEC DES INSTRUMENTS OPTIQUES (LOUPES)
PRODUIT LASER DE CLASSE 1M
ATTENTION: Observer la sortie Laser avec certains instruments optiques (par example: une loupe, un agrandisseur, ou
un microscope), d’une distance infèrieure à 100 mm peut causer des dommages occulaires.
ATTENTION:
LES CONNECTEURS OPTIQUES DEBRANCHES PEUVENT EMETTRE UNE ENERGIE OPTIQUE.
NE PAS REGARDER LE FAISCEAU AVEC DES INSTRUMENTS OPTIQUES (LOUPES)
Ce produit contient des lasers ou diodes électroluminescentes de classe 1M.
• Produit laser de classe 1M conformément à IEC60825-1:1993+A1+A2
• ATTENTION: L’ utilisation de commandes ou réglages, ou de procedures différentes de celles indiquées ici risque de provoquer une
exposition dangereuse au rayonnement.
• Prendre des précautions pour empêcher une exposition au rayonnement optique lorsque l’ appareil est retiré de son boîtier ou lorsque le
câble optique fibre est débranché de l’ appareil.
•Un rayonnement laser pourra être présent dans un câble optique branché sur cet appareil, même une fois l’alimentation coupée.
•Cet appareil est prévu pour une installation à des endroits où seul un personnel de maintenance formé accès aux cables optiques.
•Les points de branchement de tous les câbles optiques sont indiqués à la section Points de branchement et function de ce manuel.
•Les sorties et longueurs d’ onde optiques figurant à la section Caractéristiques techniques de ce manual.
Niveau de danger 1M
La bordure doit être noire et
le fond jaune

8
Fiber Information
This unit was manufactured with attention to fiber cleanliness by TKH Security Solutions USA. Beyond the
optical safety information contained in this manual, the following guidelines should be observed when working
with optical fibers.
The biggest problem is dirt!
It takes very little contamination to cause problems with optical fiber connections; cleanliness is extremely
important to proper operation of optical equipment.
1. Protect optical connectors by leaving the connector covers in place on unused fiber connections and on the
fiber tips themselves.
2. Personnel who remove and replace fibers should be equipped with a fiber cleaning kit. These are
inexpensive and can be obtained from any fiber equipment supply house. If you choose to, you can use
propanol and lint-free tissue to clean fibers.
a. Do not use isopropanol alcohol (typically called rubbing alcohol) mixed with water. This can cause
additional spots. (Caution: Pure isopropanol is very flammable! )
b. Use lintless tissues to clean fibers.
c. Clean the fiber with a folded tissue moistened with the propanol, pulling the connector tip across
the tissue, then turn the connector 90 degrees and repeat in a different spot on the tissue.
d. Don’t pull the fiber across and then push it back. This will put the dirt that was cleaned off back on
again.
e. Repeat the process on a dry, folded tissue.
3. When removing fibers, always clean them when replacing them no matter how long you had them off.
4. When connecting fibers, pay attention to the bend radius of the fibers. A general rule is to have a 3-inch
(8 cm) bend radius. A bend radius less than 3 inches is an attenuator and can cause optical signal loss.
5. Installers of fiber equipment should be equipped with the equipment manuals and an optical power meter
to measure the optical inputs and outputs in a system. An optical power meter is an inexpensive tool that
can save much time and effort in getting optical communications links up and running. Properly equipped
and trained installers can quickly determine the source of any problems that occur.
External Wiring Information
Cable assemblies with lengths external to the unit not exceeding 3.05 meters, coiled or uncoiled, may be
constructed of jacketed appliance wiring material suitable for the maximum voltage current and temperature,
rated VW-1 or FT-1 or better. Cable assemblies with lengths external to the unit not exceeding 3.05 meters,
coiled or uncoiled, and supplied by a limited power source or NEC Class 2 source of supply as defined in the
National Electric Code, ANSI/NFPA 70, may be constructed of materials rated VW-1 or FT-1 or better with no
additional requirements.

9
1 - INTRODUCTION
1.1 General description
The TKH Security USA Model 9525A is an RS232, RS422, and RS485 compatible stand alone fiber optic
modem with dual optics for drop and insert applications which can be configured in a wide range of
poll/response network architectures. The unit operates using two optical fibers to transmit and receive in the
upstream direction. A second pair of fibers is used in the downstream direction. This results in the formation
of a two-fiber daisy chain or ring.
The units may be operated in either daisy chain or fault tolerant redundant ring architectures. In addition, in
certain modes, an RS232 expansion port on the modem may be connected to a second modem with single or
dual optics to branch the network in one or two additional directions. With this capability a daisy chain
network may be set up with unlimited branches off the main trunk(s). Additionally, unlimited daisy chain
connections may be made branching off of a main fault tolerant dual fiber ring. All signals received via an
optical port and retransmitted via fiber or via the expansion port are re-timed to .01% pulse width accuracy by
a crystal controlled time-base, eliminating pulse width distortion and allowing virtually unlimited repeating.
The units have four switch selectable modes of operation: Daisy Chain Master mode, Daisy Chain Local mode,
Fault Tolerant Master mode, and Fault Tolerant Local mode. See Section 2, Installation, for a complete
description of these modes of operation.
The units may be operated in either daisy chain or fault tolerant redundant ring architectures. In addition, in
daisy chain mode an RS232 expansion port on the modem may be connected to another modem with single or
dual optics to branch the network in one or two additional directions. With this capability a daisy chain
network may be set up with unlimited branches off the main trunk(s).
The units have anti-streaming (sometimes referred to as anti-babbling) circuitry for both the optical fiber and
electrical (RS232) sides. On the RS232 side, when enabled, the anti-streaming limits the amount of time a
terminal is allowed to transmit data onto the network for each Request to Send. This is to prevent a faulty
terminal unit from monopolizing the network. On the fiber side the anti-streaming disables an optical receiver
in the event that the receiver output stays high longer than the maximum allowable time. This will prevent the
whole fiber network from being disabled by a continuous "on" failure by receiver or optical emitter. This
feature is not available when in RS422 or RS485 mode because the RTS line is not supported.
The units have nine front panel LED indicators. A POWER indicator is on solid when operating under primary
power and blinks if operating on an external gel cell battery in the case of the loss of the primary power
source. If operating in local mode, a FAULT indicator illuminates in the event of an RS232 anti-streaming
timeout. If operating in Master fault tolerant mode, the FAULT indicator illuminates if one of the two
redundant rings is broken. A relay with N.O. and N.C. contacts activates in conjunction with an illuminated
FAULT LED. A BERT indicator operates when properly receiving the BERT signal. The other six indicators serve
dual functions as selected by the indicator mode switch. In one position the LEDs indicate electrical side signal
activity. In the other position the LEDs indicate fiber port activity as well as the active fiber input port as
chosen by the priority select circuitry.
A ten-position MODES dipswitch allows the user to select the operating mode, Tx1 and Tx2 BERT Signal
Enable, and the data interface. In addition, an eight-position TIMEOUT dipswitch allows the user to select
timeouts for (or disable) the electrical side anti-streaming, the fiber activity CTS inhibit (RS232 mode), echo
cancel timeouts, and priority select timeouts.

10
The unit operates from a 9 to 15 VDC supply. The unit contains a built in battery charger compatible with a 6-
volt lead-acid gel cell battery (1.2 Amp-hour to 7 Amp-hour capacity). This battery allows from 6 to 35 hours
of emergency battery backup operation. A screw terminal connector allows the unit to connect the battery to
the unit.
The package is an anodized aluminum extrusion with painted aluminum front and rear panels. An optional
mounting kit is available for mounting in a System 9000 chassis (Model 9000KIT-5).
Table 1 - Models Available
MODELS
OPTIC
PORT
FIBER
WAVELENGTH
OPTICAL
BUDGET
9525A-S-ST
ST
62.5/125 µm
850 nm
22 dB
9525A-L-ST
ST
62.5/125 µm
1310 nm
21 dB
9525A -LD-ST
ST
09/125 µm
1310 nm
23 dB
9525A-LD-FC
FC
09/125 µm
1310 nm
23 dB
9525A-LD3-ST
ST
09/125 µm
1550 nm
23 dB
1.2 Physical Specification
DIMENSIONS
Height
Width
Length
INCHES
1.5
3.17
5.0
WEIGHT
0.875 lb.
0.4 kg
INDICATORS
POWER, TD/TX1, RD/RX1, RTS/TX2, CTS/RX2, TDEXP/RX1
PRIORITY, RDEXP/RX2 PRIORITY, BERT, and FAULT.
1.3 Environmental Specification
TEMPERATURE
Fahrenheit
Celsius
Operating
-40 to 165° F
-40 to 74° C
Storage
-40 to 185° F
-40 to 85° C
HUMIDITY
0 to 95% RH noncondensing

11
1.4 Functional Specifications
1.4.1 OPTICAL
Version S L LD LD3
Wavelength, nm 830 1310 1310 1550
Output power,
dBm, with BERT
Signal enabled, dBm
62.5 um fiber -19 -20 N/A N/A
09/125 um fiber N/A N/A -18 -18
Input power, dBm, min. for 109BER,
measured with transmitting unit
BERT Signal enabled -41 -41 -41 -41
1.4.2 ELECTRICAL (Tx and Rx)
Data Interfaces RS232, RS422, or RS485 (2- or 4-wire), switch selectable
Connectors
Primary Port DB25S
Expansion Port RJ12
Data rates 150, 300, 600, 1.2 k, 2.4 k, 3.6 k, 4.8 k, 7.2 k, 9.6k, 14.4k, 19.2k,
28.8k, 38.4k, 57.6k, and 115.2k baud (auto baud)
BER 109or better at the minimum receiver power level
Re-timing accuracy 0.01% of pulse width for repeated signals
Electrical anti-streaming
timeout selections DISABLED 1, 2, 3, 4, 8, 16, 32, and 64 sec.
Propagation Delay as
a repeater Approx. 6.5 microseconds
1.4.3 ALARM
Contact Rating 28 VDC @ 100 mA
1.4.4 POWER
Operate 8 to 15 VDC @ 180 mA
Recommended Power Supplies
9014PS (for operating temperature ranges 0° C to +40° C)
PSR 12 DC (for operating temperature ranges –10° C to +70° C)
Recommended External Battery
6 VDC, 4 Amp hour, PowerSonic Model PS640WL or equal (provides up to 20 hours
backup @ 20° C). Battery temperature range is –20° C to +50° C.

12
FIGURE 1—MODEL 9525A ENGINEERING VIEWS AND DIMENSIONS

13
2 - INSTALLATION
2.1 System Architecture
The Model 9525A can be configured into three basic network architectures. To configure the network, the modems
may be set to operate in one of four modes, characterized mainly by the internal signal routing within the modem
among the data port, the RS232 expansion port, and the two optical transmitter/receiver ports.
In addition to the routing of the data signals within the modem that characterizes its mode of operation, there are
several other operational features that are important to know. Some of these features are inherent, some are
optional, and others are absent depending on the mode of operation.
The Model 9525A can be configured into various basic architectures. They include:
a)
Simple Daisy Chain
b)
Daisy Chain with branches
c)
Fault Tolerant Redundant Ring
2.1.1 Simple Daisy Chain(s) With this architecture, the master controller lies at the end of one or two daisy
chains. See Figure 2. Note that the TX1 and RX1 ports always connect toward the master modem.
2.1.2 Daisy Chain(s) with Branches When operating in RS232 mode, the RS232 expansion port may be used to
establish additional daisy chains or branches from any of the modems in the system. To do this, connect a
Model 9525A in RS232 mode to the RJ45 expansion port of another Model 9525A, set the unit for Master
Daisy Chain operation and connect other daisy chains to it in the same way they are connected to the
primary master.

14
FIGURE 2–SIMPLE DAISY CHAIN TRUNKS FROM THE MAIN MASTER,WITH EXAMPLES OF BRANCHING USING THE EXPANSION

15
2.1.3 Fault Tolerant Redundant Ring With the architecture shown in Figure 3, all modems are arranged along
a dual fiber ring starting with the master controller modem (operating in Master Fault Tolerant mode),
looping through a number of local terminal modems (operating in Local Fault Tolerant mode), and
terminating back into the second set of optical ports of the master controller modem, completing the
ring.
In this architecture the master modem transmits data in both directions around the ring and receives
its own signal. The ring is terminated at the master modem. In other words, the data is not repeated
by the master modem, but instead it ends there.
Each local modem in the ring transmits its input data in both directions, receives from both directions,
and retransmits in both directions the data received by the optical receivers. Each local modem,
receiving data from the master from both directions around the ring, will select the data that arrives
first and output that signal to the data port. If the transmission is interrupted in that direction, the
modem will automatically select the data from the other direction. The master modem also receives
data from both directions from each of the local modems, and selects the first arriving data in the
same manner.
In this mode, the master will normally receive an echo of its own signal. To disable the echo, select the
ECHO OFF on the Mode switch bank. Enabling the “ECHO OFF” is imperative for RS485 2-wire
operation.
2.2 Modes of Operation
To set up a modem into one of its four operating modes, the user selects one of four combinations for
switch sections 1 and 2 of the MODES dipswitch.
These four modes are characterized by the specific signal routing within the modem, shown in Figure 4.
The following sections include a detailed description of each mode described in Figure 4.
2.2.1 Master Daisy Chain Mode
In this mode a TD input to the data port is transmitted out via the TX1 and TX2 optical ports and out
the expansion port as RDE in RS232 format. With the
INDICATORS mode switch in the up position, a TD input will cause the TX1, TX2 and RDE indicators to
illuminate.
Conversely, an optical input via the RX1 or RX2 optical port or an RS232 input via the expansion port will
be output via the DB25 port as RD.

16
FIGURE 3–FAULT TOLERANT RING ARCHITECTURE

17
In this mode, priority select is not used. This mode is normally used in a network with numerous modems in local
daisy chain mode, where the master can act at the head of two separate daisy chains (or more, if the expansion
port is used).
FIGURE 4–INTERNAL SIGNAL ROUTING FOR EACH OPERATING MODE

18
2.2.2 Local Daisy Chain Mode
In this mode, there is a specific "upstream" and "downstream" data direction. Specifically, the TX1 and
RX1 ports communicate upstream with the master controller and the TX2 and RX2 ports communicate
downstream with the next modem on the daisy chain. The local daisy chain mode is not fault tolerant.
Optical data received from the master via RX1 is re-timed, retransmitted downstream via the TX2 port
and output as RD on the data port. Anti-streaming on the RX1 port is disabled because it would serve
no purpose. Optical data received from the next modem downstream via the RX2 port is re-timed and
retransmitted upstream to the master controller via the TX1 port. Data received via the expansion port
input TDE from a modem feeding a branch, and from the TD input of the data port are ORed with the
data from the RX2 port to be transmitted back to the master via the TX1 port.
Antistreaming is an option on the RX2 port in this mode when operating in RS232 data mode.
2.2.3 Master Fault Tolerant Mode
This mode is virtually the same as the master daisy chain mode explained in Section 2.2 with these
exceptions: Because this is a fault tolerant mode, data will normally be received via both optical ports,
skewed slightly in time of arrival. Therefore, in this mode the priority select circuitry is employed to
choose only the data that arrives first. Secondly, the expansion port is not available in this mode.
2.2.4 Local Fault Tolerant Mode
This mode is used for all the local modems serving the many terminals around a fault tolerant dual
fiber counter-rotating ring. In this mode optical data received via both optical ports is selected based
on the earliest arrival (see Priority Select, Section 2.1.4), and routed to the RD output of the data port
and the RD output of the expansion port.
Optical data received via RX1 is retransmitted via TX2. Optical data received via RX2 is retransmitted
via TX1. These functions serve to regenerate and repeat data traveling both directions on the dual
optical ring. Data input via either TD on the RS232 port or TDE on the expansion port is ORed and
transmitted in both directions on the dual fiber ring.
2.3 Operational Features and Considerations
In addition to the signal routing that characterize each mode of operation (Section 2.2) the following
features of operation are incorporated as either basic indispensable functions or as performance
enhancements.
2.3.1 Electrical Side (Data Input) Anti-Streaming (RS232 mode only)
The electrical side anti-streaming feature, when enabled, limits the time that a terminal unit may
transmit data with a single request-to-send (RTS) enable. This feature is designed to prevent a
terminal unit from monopolizing the network if a terminal unit fails in a mode causing continuous
transmission. When the RTS input is set high (TRUE), the RS232 side anti-streaming counter is armed.
When data transmission begins, the timer begins, allowing the terminal to transmit data for a period of
time up to the time-out limit. When the terminal unit stops transmitting it must immediately set the
RTS low, (FALSE), resetting the timer. If the terminal continues to transmit data to the modem past
the timeout period, transmission from the modem will cease, the CTS will go Low, the FAULT indicator
will illuminate, and the alarm dry contact relay will activate.

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To use this feature an active RTS signal is required. If the RTS input cannot be actively controlled, the
electrical side anti-streaming feature must be disabled. MODES switch numbers 1, 2, and 3 allow the
user to select one of seven timeout periods, or disable the feature. To select a timeout, calculate the
longest transmission burst expected by the terminal and pick the next highest timeout period. If this is
not practical in your system, just disable it.
2.3.2 Optical Side Anti-Streaming
The optical side anti-streaming feature, when enabled, disconnects an optical receiver from the circuit
in the event that the receiver's output goes high for a period longer than would be expected in normal
data flow. This may occur due to a receiver failure, a transmitter or terminal equipment failure, or if
the receiver input is left open to strong ambient light (850 nm versions only). The anti-streaming
feature will prevent such an error from "locking up" the network.
The circuit works as follows: As long as the data is high (optical power present at the receiver) the
timeout proceeds. Whenever the data goes low, as it does for all normal zeros, the timeout resets. As
long as the data does not contain a long string of continuous ones that exceeds the timeout period,
the anti-streaming will not be triggered. If there are too many ones in a row or if there is a failure that
leaves the receiver output constantly high, the receiver output will be disconnected from the circuit
and the FAULT indicator will illuminate. Mode switch numbers 4 and 5 allow the user to select among 3
timeouts or to disable the feature. The longest timeout selection is sufficient to not trigger an optical
side anti-streaming timeout for continuous 8 bit ASCII characters ("quick brown fox") at only 150
baud. Faster data rates allow the use of a shorter timeout.
2.3.3 Clear to Send Inhibited by Optical Side Activity
Another optional feature, enabled or disabled by MODES switch number 6, causes the disabling of the
Clear-to-Send (CTS) control line output in the presence of fiber side data activity. Normally the system
software will preclude such an occurrence, but as a safeguard, this feature will prevent a terminal from
interfering with data already traveling on the optical trunk or ring either from the master or from
another terminal. The circuit uses the “Priority Select” timers to determine the CTS disable period.
Whatever Priority Select timeout is selected applies. The selected rates should be sufficient to keep
CTS disabled for a period of one byte. For ASCII character transmission at rates below 600 baud, this
feature should not be used.
2.3.4 Priority Select
Priority Select is enabled automatically in both Master and Local Fault Tolerant modes (see Sections
2.2.3 and 2.2.4). The priority select circuitry automatically selects the data that arrives first via optical
port RX1 or RX2. In normal operation, since the master transmits both directions on the ring, each
terminal on the ring will receive data from both directions. The optical signal that arrives first will be
selected by the priority select circuitry and output via the RS232 ports as RD and RDE. If the
data transmission in the first direction fails it will automatically select the data coming from the other
direction the next time it is transmitted.

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2.3.5 Echo Cancel
There is a circuit that prevents data transmitted around a ring by a unit operating in Master Fault
Tolerant mode from being output as received data (RD). This data would normally be termed an ECHO.
Some software is intolerant of echoed data.
Echo cancel is mandatory when operating in RS485, 2-wire mode to prevent data corruption, optional
in other interface modes.
In addition, when operating in RS485 2-wire mode it is possible to have the electrical data corrupted
due to the fact that the transmit data input and the echoed data output occurs on the same pair of
wires.
2.3.6 Redundant Ring Break Detector
When a unit is operated in Master Fault Tolerant mode, a circuit is automatically engaged that will
detect if either or both of the signals transmitted in opposite directions around the dual fiber ring fails
to arrive back at the master unit, indicating a re-transmission failure or fiber break in one or both of
the rings. If this occurs, the FAULT LED will illuminate and the dry contact relay will activate.
Examining the RX1
and RX2 indicators, or running the simple BERT test (see 2.3.7), should reveal which ring has the
problem.
2.3.7 BERT
The unit has a built-in rudimentary BERT signal generator and detector. This feature may be used off-
line such as in system installation or in a troubleshooting session to quickly indicate the integrity of a
transmission path in the network. If properly received, the green BERT indicator will illuminate steadily.
Any one unit in the network at any one time may be chosen to initiate the BERT signal. If initiated by
the master unit in a fault tolerant ring, removing the fiber from one, then the other, output port will
allow for the separate testing of each ring. The blinking of the BERT indicator during normal data
transmission is meaningless and should be ignored. The indication of this LED is only valid while a
BERT generator is enabled. The
BERT test signal may be transmitted via either or both optical ports as enabled by switches 3 and 4 of
the MODES dipswitch.
2.3.8 Remote Master Mode Selection
The unit may be selected to change from Local to Master mode by attaching an external switch closure
between the G and M terminals of the 5-position terminal block shared with the alarm relay contact
outputs. Alternately, an active LOW TTL logic level may be input to the G terminal. With this feature,
different units in a network may serve as the master at different times. To use this feature, the
Master/Local switch, position 1 on the MODES dip-switch, must be in the UP, or OFF position (Local
Mode selected).