AT&T Bell System 1A Manual page 12

SECTION
252~
129-100
the second and all other even-numbered groups
shall contain five busys (0005) per scan.
MODE Switch
2.54 This switch, when operated
to
RUN, allows
the CCU to be operated in a normal manner.
When this switch is set to TEST, the CCU
disconnects the 401J-type data set and substitutes
an internal test data generator.
20 Circuit Pack Lamps
2.55
Fifteen of these 20 lamps mounted on the
MSL-20 circuit board indicate the status of
various logic elements in the CCU.
PS4, PS3, PS2, and PS1 Lamps
2.56 These lamps, when lighted (as indicated in
Table A by an• X), indicate the number of
the channel whose information is being sent to
the TTY. The channel number is represented by
binary bit positions, as shown in Table A.
G5, G4, G3, G2, and G 1 Lamps
2.57
These lamps, when lighted (as indicated in
Table B by an X), indicate the number of
the EOG signals received from each RSEU. These
lamps light cyclically for each channel or RSEU
scan. The data group number is represented by
binary bit positions, as shown in Table B.
WRT 8
Lamp
2.58
This lamp, when lighted, indicates the status
of the CCU memory switching unit. When
lighted, the lamp indicates that RSEU data is being
read into memory B; therefore, any data being
read out is from memory A and vice versa.
TABLE A
STATUS OF PS4, PS3, PS2, AND PS1 LAMPS
CHANNEL
LIGHTED LAMP
1 2 3 4 5 6 7 8 9
10 11 12 13 14 15 16
PS4 X X X X X X X
X
PS3 X X X X
X X X X
PS2 X X X X X X X
X
PSl X X X X X
X X X
TABLE B
STATUS OF G5, G4, G3, G2, AND G1 LAMPS
GROUP
LIGHTED LAMP
1 2
3 4 5
6 7 8 9
10 11 12 13 14 15 16 17 18 19 20
G5 X
X
X X
G4 X X X X X X
X X
G3
X X X X X
X
X X
G2 X X X X X
X
X X
X X
Gl X X X X X X
X X
X
X
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