- 139 -
from speech channels.
Lowpass Filter, 2kHz, used in EPlM/ll, EPlM/12 to limit
the bandwidth of telephone speech on the control line
BP-WRT to prevent interference with digital switching
tones. Complementary to FL3/2l. CHl/18C, pegs 35, 40.
DD 1969. WITHDRAWN.
Lowpass Filter, 5kHz, used in EPlM/ll to limit the
bandwidth of programme over the BH-BP reserve line when it
is being used for digital switching. CHl/18C, pegs 35,
39. DD 1969. WITHDRAWN.
Lowpass Filter, 15kHz, used in CD2M/2. Contains two
lowpass filters and audio amplifiers. Printed board with
25 way ISEP plug. DD 1971. DDMI6.274(76). OBSOLESCENT.
Lowpass Filter, designed to replace FLP/5A at HF
transmitting stations. Has fixed cut off frequency of
6. 3kHz and 600Q input and output impedances (unbalanced).
Intended for use with transistor amplifiers. CH2/2.
TCPD 1971. OBSOLESCENT.
Lowpass Filter used in PCM Decoder BAl/5. Special Imhof
l33mm CDX panel with up to 13 x FL4/50. DD 1971.
Lowpass Filter used in PCM Coder BAl/4. Special Imhof
l33mm CDX panel with up to 13 x FL4/49 and 1 x FL4/50.
DD 1971. OBSOLESCENT.
Lowpass Filter, used to restrict the audio bandwidth of
long wave and medium wave transmitters to 5kHz,
approximately. In band loss approximately l3dB; can be
used in conjunction with AM7/4 and attenuator. CHl/18A.
DD 1972. OBSOLESCENT.
Lowpass Filter, used in EP8/5 to filter output signal.
CHl165A. Superseded by FL4/69. DD 1975. OBSOLESCENT.
Lowpass Filter, used in EP8/4 to filter input signal.
Printed circuit board to fit BMM general purpose panel.
Superseded by FL4/68 and FL4/68A. DD 1975. OBSOLESCENT.
Filter, Lowpass, Linear-phase, 3.6Mc/s, for removing noise
coded FI4/50l. DD 1957/61. DD Spec 9.4. OBSOLESCENT.
Similar to FL4/50l but fitted with coaxial plugs instead
of flying leads. Originally coded FI4/50lA. DD 1957/61.
4.75kc/s. Used with translating equipment for
transmission over transatlantic telephone cable.
A indicates pre-emphasis 2.5kc/s (sender) and
B indicates de-emphasis at 2.5kc/s (receiver) to
intermodulation effects. Originally coded FI4/S02.