OPTICAL SYSTEMS DESIGN
DOC ID: 10104804.doc
OSD840 OPERATOR MANUAL
PAGE 7
1.5
PRODUCT DESCRIPTION
The OSD840 series is a high-quality digital video, Ethernet, audio and data optical fiber transmission
system. The system consists of the OSD840T and the OSD840R, which are designed to be used as a
pair. The system provides one-way transmission of PAL, NTSC or SECAM video, plus full-duplex
transmission of two audio, three data channels, one relay channel and a 10/100 Base-T Ethernet
connection via the RJ45 connector.
The OSD840T accepts one analogue composite video input signal and two analogue audio input signals
along with three digital data input signals, one relay contact signal and a 10/100 Base-T Ethernet
connection. The video signal is converted to digital with 10-bit resolution, while the audio signals are
converted using 24-bit resolution so as to preserve the quality of the input signals. The resulting digital
signals are multiplexed and transmitted as a digital bit-stream through the fiber. The OSD840T also
includes an optical receiver section that decodes the digital signal transmitted by the OSD840R, to
provide audio, data and relay output signals including Ethernet. The audio channels can be balanced or
unbalanced at 775mV nominal level and operate over a 22kHz bandwidth. The second audio channel
can also be configured as a front-panel-accessible 2-wire intercom suitable for commissioning and
servicing or for permanent use. The data channels can be RS232, TTL, RS422 or RS485 on one
channel and RS232 on the other channel and may operate from DC to 400kbps. User adjustable
turnaround times are provided for RS485. The fourth channel is a full duplex contact input/relay
output channel for control/alarm purposes. The OSD840T control signal receiver provides adjustment
free operation over the full optical range of the unit.
The OSD840R incorporates a high performance optical digital receiver for incoming video, audio, data
and Ethernet signals, and a transmitter that outputs a digital optical signal consisting of two audio
signal, three data channels, 1 relay channel and Ethernet. The unit provides a constant video output
level which is independent of link loss, and the audio and data section of the OSD840R is also
adjustment free over all link lengths. Audio and data signal interface levels and impedance’s are the
same as those of the OSD840T.
The OSD840T and OSD840R are available in two physical configurations: card or stand-alone case.
The card versions are designed to fit the 3RU-high 19” OSD370 chassis, which allows multiple OSD
card products to be conveniently powered from and located in the one chassis. The stand alone case
versions are intended for isolated use and require an external power source.
The OSD840 system can be used with any standard multi-mode optical fiber, and is available
optionally for single-mode fiber use. A Wavelength Division Multiplexing version is also available to
allow the use of a single fiber for transmission and reception.
