4
opposite device. Alarm status of opposite device can be detected only at framing
mode.
LOS
：
E1 Alarm indicator lamp for code missing in optic line. Constantly lightening indicates
the alarm with local device. Flash indicates the alarm with opposite device.
LOOP
：
Indicator lamp of loopback test status. When local device is at a loopback status, the
lamp flashes. When local device is not at a framing mode, it is unable to detect
whether opposite device is at a loopback test status.
PTOK
：
Indicator lamp of pseudo-random code test. When the device is at a loopback status,
pseudo-random code test can be made. If this lamp is constantly lightening, it
indicates that pseudo-random code passes the test.
Rear panel
：
Rear Panel of IT-7304-PC/AC
220V AC
：
AC power jack.
OFF ON
：
Power switch. When the ON button is pressed down, the power supply is turned
on.
V.35: V.35 interface, with a M34 cored jack.
TX RX: Receiving/sending jack of optical fiber, with TX as the sending terminal and RX as
the receiving terminal.
There is a coded switch S5 on the panel, which is used as the system configuration switch to
set such functions as clock, time slot, phase, loopback and pseudo-random code test etc.
Wherein, S5.1 and S5.2 are clock settings.
S5.1
＝
OFF, S5.2=OFF
：
network clock at V.35 interface (Received Recovered).
S5.1
＝
OFF
，
S5.2
＝
ON
：
network clock at the optic fiber interface (Received Recovered).
Remote time slot setting can be tracked only at this status.
S5.1=ON, S5.2=OFF: invalid
S5.1
＝
ON
，
S5.2
＝
ON
：
using local crystal OSC generating clock
S5.3: time slot setting
S5.3
＝
OFF
，
using remote time slot setting (valid only when S5.1
＝
OFF
，
S5.2
＝
ON)
S5.3
＝
ON
，
using local time slot setting
S5.4: for V.35 receiving clock phase selection
S5.4=OFF, using positive phase
S5.4=ON, using negative phase
S5.5: Local loopback setting (optic interface in direct loopback), ON valid.
S5.6: Local digital loopback (V.35 interface loopback), ON valid.
S5.7: Remote digital loopback (V.35 interface loopback), ON valid.
Valid at framing mode (0-time slot unused).
S5.8: Pseudo-random code test, ON valid, and valid at loopback status.