Marconi Instruments 2955 - Page 24

INSTALLATION
Fig,
2-3
ACCESSORY
socket contacts (as
viewed
from
the front)
Selection
logic
on
contacts
6,
1 and 3 enable
the
instrument
to
detect and
recognise
the
connection
of an
external accessory. The
appropriate
contacts are
at TTL
levels and
are
active low
(L) as
follows;-”
Accessory
6 1
3
Nothing
connected H
H
H
Headset
(press to talk)
L L
H
External power: Auto zero L
H
L
External power;
Peak
power
L
H
H
External power:
RMS power
H H
L
Psophometric
filter: C-MESS H
L
L
Psophometric filter: CCITT
H L
H
Spare L L
L
A
3.0
m lead
assembly
44990-8
14K
is
available as
an
optional
accessory.
RF IN/OUT
SOCKET
Where
conformity
with
the radio frequency
interference
limits
specified
by
VDE
(Verband Deutscher Electrotechniker) is
required, a
double-screened
lead
assembly
43137-052Y is available
as
an
optional accessory.
2-6
46881-622N
Apr.
83