Eddystone 990R - Page 18

Line Output .
This output is
marked
”6000"
and
provides
a
maximum
of lOrnW
for
connection
to
remote
lines.
The
centre-
tap
(CT) can
be
left floating: or
alternatively
earthed
to
provide
a
balanced
output.
The
secondary
winding is
electrostatically
screened from the
primary.
It
should
be
noted
that
this
output is
short-circuited (in absence
of
signal)
by
a
pair
of relay
contacts
when
the
muting facility
is
in
use.
Consideration
should
there-
fore
be
given
to
inclusion
of
a
suitable pad to
isolate
this output
when making
direct
connection
to
Post
Office
lines.
Mute
Indicator .
One pair
of
contacts
on
the
muting relay
is
arranged so
that the circuit
across
th$
"MUTE
INDICATOR"
terminals
will
be closed when the
receiver
is
running
in
the
muted
condition.
The
circuit
will
open (l)
on
receipt
of
a signal
,
(2)
if the muting
is
switched
to
"off", or
(
3
)
if the
receiver supply is
removed.
A
lamp
(with
external
supply)
can
therefore
be installed to
indicate
to
a
distant
monitoring position
that
the remote
receiver
is
operational but
muted. The
lamp will
extinguish on
receipt
of a
signal.
If additional
signalling
facilities are
required,
it
is a simple
matter
to
replace
the lamp
with
a
relay
and use
the
contacts on this
to
control
other
indicators.
For
example,
a
SPDT relay
could
be
arranged
to illuminate
a
lamp
when
the circuit
is
quiet
and to operate
a
call
buzzer
when the
channel is
in use.
The internal
relay
contact
is
wired such
that one of
the two terminals
is
permanent-
ly
earthed and
the
other
becomes
earthed in
the
absence of a
signal (with
the
MUTING
SWITCH
In
the
"OH" position).
Earth
Terminal .
Bond
to
frame
of
rack
when
receiver is
installed
as a
rack-mounted
equipment.
17
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