Black Box ME375A-R2, Руководство пользователя, Страница: 19 / 34

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ASYNC/SYNC 2-WIRE SHORT-HAUL MODEMS
Table 4-1. Front-Panel Controls and Their Functions
Control Function
DIG Press this Local Digital Loopback button to cause the local A/S2W
SHM to loop received data and clock signals from the line back
out of its own transmitter. This is equivalent to activating remote
digital loopback (see below) on the remote unit. Press this button
again to terminate local digital loopback.
ANA* Press this Local Analog Loopback button to cause the local
A/S2W SHM to loop its transmitter output back into its own
receiver. Press this button again to terminate local analog
loopback. While the A/S2W SHM’s LLB jumper is set to EN
(enabled—see the third part of Table 3-1 on page 15), you can
also control this type of loopback by raising and lowering the LL
signal from the DTE on the appropriate pin for your interface.
REM* Press this Remote Digital Loopback button to cause the remote
A/S2W SHM to loop received data and clock signals back out of
its own transmitter. (Data Set Ready goes low when this
happens.) Press this button again to terminate remote digital
loopback. While the A/S2W SHM’s RLB jumper is set to EN
(enabled—see the third part of Table 3-1 on page 15), you can
also control this type of loopback by raising and lowering the RL
signal from the DTE on the appropriate pin for your interface.
PATT Press this Pattern button to cause the local A/S2W SHM to send
the remote unit a continuous Bit Error Rate test pattern. Press this
button again to stop sending the test pattern.
RESET Carefully press a long thin object such as a tack or the end of a
paper clip into this recessed switch to reset the A/S2W SHM. Do
this to clear abnormal conditions (the indication of an error
condition, for example) instead of unplugging the unit and plugging
it back in.
*The ANA and REM buttons are not affected by the settings of the RLB and
LLB jumpers (see the third part of Table 3-1 on page 15). Even if those
jumpers are set to DIS (disabled), you can still control loopback testing with
these buttons.