FLl/l,lA
FLl/2
FLl/3
FLl/4
FLl/5
FLl/6
FLl/7
FLl/8
FLl/9
FLl/lO
FLl/ll
FLl/12
- 127 -
FLl
FLl MISCE"LANEOUS FILTERS
Notch Filters, ~2Mc/s to 70Mc/s and 70Mc/s
respectively us~d for test purposes on
equipment for n)tching out any particular
DD 1959.
WITHDRA' IN .
to 100Mc/s
translating
f req uency .
Used on VF Swi:ching System. Consists of bandpass,
highpass and band~top filters. DD 1959. WITHDRAWN.
Bandstop Filter,
System. DD 1959.
l640c/s-1740c/s,
WITHDRAWN.
on VF Switching
used
Bandstop Filter flrst used VF switching system between
Glasgow and Kirk O'Shotts. 600~ insertion loss greater
than 50dB from 1570Hz-1710Hz. DD 1959. DD Spec 2.140.
OBSOLESCENT.
Bands top Filter ~iving about 40dB attenuation in narrow
band centred on 1).125kHz to prevent whistle interference
from television line frequency when sound and television
programmes are broadcast simultaneously from the same
studio. l52mm x l27mm x l52mm. DD 1960. DD Spec 2.131.
OBSOLESCENT.
Band and High Pas~ Filter first used on VF Signalling
System between GliSgOW and Kirk O'Shotts. 483mm x l33mm.
Includes bandpas~ filter (1640Hz-1740Hz) and highpass
filter passing ill frequencies above 1kHz. Filters
selected by sla~e relays operated by relays on PAl/22.
DD 1960. DD Spec 2.147. OBSOLESCENT.
Notch Filter us~d on FM Translator EP7/l.
WITHDRAWN.
DD 1960.
Bandstop Filter flrst used on VF Signalling System between
Glasgow and Kirk O'Shotts. 483mm x 89mm. 600~ insertion
loss
greater
thin
40dB
from
1670Hz-1740Hz.
DD 1960.
DD Spec 2.146. O~SOLESCENT.
Bandstop 500Hz ~ilter to prevent 500/20Hz ringers on
speech circuits b~ing talked up when music is fed for cue
purposes over theie lines. l2lmm x 83mm chassis. Three
mounted on PN3/26. DD 1961. DD Spec 2.184. OBSOLESCENT.
Bandstop 700Hz Fi.ter to prevent 700Hz signal from a voice
frequency passin~ through PA19/l and giving a false
indication. Th:ee mounted on PN3/26. DD 1961.
DD Spec 2.180. QiSOLESCENT.
Similar to FLl/lO but for 600Hz. DD 1961. DD Spec 2.179.
OBSOLESCENT.
Band and HP ],ilter used at receiving terminal on
Bristol-London V:/ Switching System. BP filter accepts
100c/s wide band based on 1.69lc/s. HP filter passes
above lkc/ s. DD: .962. DD Spec 2.206. OBSOLESCENT.

27