FLl
- 128
FLl/13
Bands top 500Hz
speech circuits
purposed on
OBSOLESCENT.
Filter t) prevent 500/20Hz ringers on
being talted up when line is used for cue
CHl/18C.
DD 1962.
DD Spec 2.193.
FLl/14
Switchable Lowpass and Bandpass Filter for balanced 600~
circuits.
Used for measurements.
Portable.
Positions:
(a) straight through, (b) LP filter with 10c/s cut off,
(c) BP filter, 400c/s to 10kc/s. DD 1963. DD Spec 2.213.
OBSOLESCENT.
FLl/15
Notch Filter, 10.7MHz, used with FL2/4 in IF section of FM
translators. Printed bDards in copper box. DD 1964.
DD Spec 5.75. OBSOLESCE~T.
FLl/16
Selective Filter used i~ Carrier Drive Panel (PA5M/2A,
PA6M/2B). Resonates at 2.6kc/s or 5.6kc/s and 8kc/s.
CHl/18C. DD 1964. DD S~ec 2.240. WITHDRAWN.
FLl/17
Notch Filter used on BAl~/9. 483mm x
helical resonators ccnnected in
OBSOLESCENT.
222mm panel with 6
pairs. DD 1965.
FLl/18
Directional Filter, 20dB, Band Ill,
return loss at VHF. Printed
OBSOLESCENT.
for measurement of
board.
DD 1966.
FLl/19
Directional Filter, 20dB, Bands IV and V, for measurement
of return loss at UHF. Printed board. DD 1966.
OBSOLESCENT.
FLl/19A
As FLl/19 but with
straight connectors.
rigl.t angle connectors
DD 1970. DD Spec 6.168.
instead of
WITHDRAWN .
FLl/20
Directional Filter, 10dB! Bands IV and V, for measurement
of return loss at tHF. Printed board. DD 1966.
OBSOLESCENT.
FLl/20A
Similar to FLl/20 bu1. with
connectors instead of HNC. Used
low level output 1:0 test
DD Spec 6.162. OBSOLESCJ:NT .
Sealectric pattern 17
in C02/54l to provide a
RC5M/50l.
DD 1969.
FLl/2l
Carrier Filter, Channels 2, 3, used in EP2/l. Contains
an amplifier for the output of Channel 1 combining unit, a
LP filter and a HP filt4~r for filtering out the upper
sideband of Channel 2 llodulator (5.6kHz carrier) and the
lower sideband of Channl!l 3 modulator (5.4kHz carrier).
CHl/18C,
pegs
15,
of3.
DD 1966.
DD Spec 2.281.
OBSOLESCENT.
FLl/22
Channel 4 Carrier Fil:er used in EP2/l. Contains LP
filter to pass Channels ..-3 and HP filter to pass Channel
4, with a relay for swit~hing out Channels 1-3 to provide
a music circuit. CHL/18C, pegs 15, 44. DD 1966.
DD Spec 2.282. OBSOLESC~NT.
FLl/23
Longitudinal Interferen~e Filter used in microphone input

28