Colour Display System SEMIGRAF 240 - The history of Ericsson

Fig. 16
Housing for one line repeater, right. On the left is
shown a cut-away view of a housing for a remotely
fed branching terminal with the multiplex equipment
at the top and the line repeater and DC/DC
converter below
Fig. 17
The line repeater shelf for rack mounting accommodates
three repeaters. The connection to the
power input adapter and the termination box for
coaxial cable can be seen above the various repeaters
dependent on the type of cable and input
points for the power feeding.
The application possibilities described
above are of great economical importance
when the systems are used in
public telecommunication networks,
and they are often an essential condition
for their use in military networks, railway
systems and pipeline projects.
Service channels
Systems ZAX 120-480 T also contain two
extra carrier channels for service
purposes and the transmission of special
functions. These connections constitute
a complement to the systems
when the systems are installed for railways,
power lines or pipelines and can,
for example, also be used for an alarm
telephone when the system is run along
a motorway.
These channels, with a bandwidth of
approximately 4 kHz each, are placed in
the frequency range between the edge
of the frequency band of the directional
filter and the regular line band for the
transmission direction in question, fig.
4. One of the channels is only intended
for speech connections when servicing
and maintaining the system. A portable
loudspeaking telephone containing
equipment for sending and receiving in
both directions of transmission is provided
for use on this channel.
The telephone, fig. 15, which is fed from
a dry battery, is of the "handy-talkie"
type and can be connected direct to the
system line repeaters. The other channel
can be used for, for example, an
omnibus speech connection or for voice-frequency
telegraphy, data transmission
etc. as required.
The additional equipment for this channel
is permanently housed in the system
line repeater housing, and is powered
from the line.
Mechanical construction
The equipment in a terminal or powerfeeding
intermediate repeater station is
mounted in racks, whereas the dependent
intermediate repeaters are
mounted in sealed steel housings,
which are designed for burying in the
ground.
The terminal rack, which can be the LM
Ericsson M4 or M5 rack, accommodates
three completely separate line systems
for ZAX-ZAC 480 T. Each system has its
own power feeding in the form of a converter
from battery voltage to 12 V,
which is the operating voltage of the
equipment. Test outlets, alarm indicator
and a switch for changeover from Aalarm
to B-alarm are provided on the
front of each unit.
The line equipment in a terminal comprises
line matching, line repeater, remote
power feeding unit, central frequency
generation and power supply
unit.
These various functions are combined
to form shelves or shelf stacks, which in
principle makes possible arbitrary placing
in the rack or combination with other
equipment, figs. 6, 13 and 17.
The intermediate repeater station for
outdoor installation consists of a line
repeater mounted in a sealed housing
made of steel. The housing is available