UN21/23
UN21/24
UN21/24A
UN21/25
UN21/26
UN21/26A
UN21/27
UN21/27A
UN21/28
UN21/29
- 409
UN2l
DD 1970. WITHDRAWN.
Reserve Programme Switching Relay Unit used at Open
Unviersity unattended MF transmitters to switch between
main and reserve feeds of programme. Fitted between main
and reserve feeds of programme. Fitted with override key.
Controlled by UN2l,26. CHI/52 with same index pegs as
UN2l/24, UN2l/25. SCPD 1970. OBSOLESCENT.
Reserve and Opt out Switching Relay Unit used at
studio centres to switch between main and reserve
programme, and for opting out either or both
networks, for Open University purposes. Override
reserve switching. SCPD 1970. OBSOLESCENT.
regional
feeds of
of two
key for
Version of
network.
Switching
WITHDRAWN .
UN2l/24 for use at sub-centres not on R34
Associated with Open University (Radio) Tone
System. CHI/52, pegs 1, 2, 3. DD 1970.
Network Splitting Relay Unit used in Broadcasting House
London Control Room for separating the MF and VHF
distributions of R4 for Open University programmes.
CHI/52 with same index pegs as UN2l/23, UN2l/24.
SCPD 1970. OBSOLESCENT.
Control Relay Unit (Transmitters) used at Open University
unattended
MF
transmitters
to
control
UN2l/23
and
transmitter starting, and to prevent Automatic Line Tests
from starting unattended transmitters. CHI/52, pegs 1, 2,
4. SCPD 1970. OBSOLESCENT.
Simplified version of UN2l/26 to provide remote monitoring
indication
and
alarm,
but
not
executive
action,
at
attended transmitters. CHI/52, pegs 1, 2, 4. SCPD 1970.
OBSOLESCENT.
Control Relay Unit (Regions) used at regional studio
centres to control reserve programme switching via
UN2l/24, but the insertion of the appropriate monitoring
tones in the regional distribution of a network. CHI/52
with same index pegs as UN2l/26, UN2l/28. SCPD 1970.
OBSOLESCENT.
of UN2l/27 for use at sub-centres
Associates with Open University
System. CHI/52, pegs 1, 2,
not on R34
(Radio) Tone
41. DD 1970.
Version
network.
Switching
WITHDRAWN.
Control Relay Unit (Origin) used in Broadcasting House
London Control Room to control the insertion of the
appropriate monitoring tones at the point of origin of a
network for Open University purposes. CHI/52, pegs 1, 2,
4 as for UN21/26, UN2l/27. SCPD 1971. WITHDRAWN.
Splitting Network Relay Unit, Stereo, similar to UN2l/25
but with extra relays for separate switching of stereo A
and B channels. CHI/52, pegs 1, 2, 3 as for UN2l/25.

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