INTRODUCTION:
The Async/Sync 2-Wire Short Haul Modem (A/S2W SHM) operates synchronously or asynchronously at high speeds (600 bps to 128 Kbps) and in full duplex over one pair of dedicated telephone lines. It has a range of 3.4 miles (5.5 km) over 26-AWG
wire. The A/S2W SHM operates in full duplex over 2 wires by using the adaptive "echo-canceling" technique. Because it also uses 2B1Q line coding, it can achieve the range mentioned above no matter what the data rate is.
The A/S2W SHM incorporates interface circuits for the terminal/computer, an adaptive echo-canceler, an automatic adaptive equalizer, a modulator, and a demodulator. It is couples to the telephone line through an isolation transformer, which protects
against AC or DC overvoltages. The protection circuitry would enable the unit to operate even if DC were accidentally connected to the line.
The A/S2W SHM has diagnostic capabilities: It can perform local analog loopback and local and remote digital loopback. The operator at either end of the line may test both modems and the line in the remote digital loopback mode. Loopback can be
controlled with either the unit's front-panel pushbuttons or signals passed through the DTE (PC, data-terminal) interface.
CONFIGURATION AND INSTALLATION:
PLACEMENT:
The Async/Sync 2-Wire Short Haul Modem is designed to be placed on a tabletop, shelf, or bench, and is delivered completely assembled. (No provisions are made for bolting the A/S2W SHM to any surface). The A/S2W SHM should be installed
within 1.5 m (5 ft) of a grounded AC outlet and must be situated within 25 ft. (7.6 m--ME376 models) or 50 ft. (15 m--ME375models) of the associated data terminal. Allow at least 36" (90 cm) of clearance in front of the unit so you can access it
during operation and maintenance. Make sure that there is at least 4" (10 cm) of clearance behind the unit for signal lines and interface cables.
SETTING THE INTERNAL CONTROLS:
Before you install any cabling and definitely before you plug in the unit, you should set the Async/Sync 2-Wire Short Haul Modem's internal controls to suit your application. (If you don't feel comfortable about doing this yourself, get an experienced
technician to do it or to help you). To access the internal controls, first make sure the unit is disconnected from the AC power, then unscrew the two screws on the unit's rear panel and slide the bottom half of the unit out form beneath its cover.
CONNECTING THE DATA CABLES:
1. Connect the twisted-pair transmission line to the two clips marked LINE (or Pins 4 and 5 of the RJ-45 connector) and (optionally) the cable shield to the clip marked GND (or Pin 2 of the RJ-45 connector). If you are using the connecting line to
the clips, refer to the Wire-Insertion Details on the first page. We highly recommend that for your transmission line you use twisted-pair cable capable of supporting high data rates, especially Category 3 or better, in order to prevent crosstalk.
Our product code for a type of cable that fits the bill, bulk unterminated Category 5 UTP, is EYN717A (specify the length you want).
2. Run the DTE-side cable from the DTE to the A/S2W SHM. If your A/S2W SHM is an ME375 model, this cable should be straight-through-pinned and 50 or fewer feet (15.2 or fewer meters) long; it should also have a DB25 female connector on
the DTE end and a DB25 male connector on the A/S2W SHM end. (Our product code for this type of cable is ECM25C; specify the length you want and "male-female" genders).
If your A/S2W SHM is an ME376 model, this cable should be straight-through-pinned and 25 or fewer feet (7.6 or fewer meters) long; it should also have a 34-pin M-block male connector on the A/S2W SHM end. (Our product code for this type
of cable is EYN450; specify the length and genders you want).
OPERATION:
On page 1, shows the front panel of the Async/Sync 2-Wire Short Haul Modem, including all of the controls and LED indicators mounted on it. These controls and indicators are described below.
DIG:
Press this Local Digital Loopback button to cause the local unit to loop received data and clock signals from the line back out of its own transmitter. This is equivalent to activating remote digital loopback on the remote unit. Press this button
again to terminate local digital loopback.
ANA*:
Press this Local Analog Loopback button to cause the local unit to loop its transmitter output back into its own receiver. Press this button again to terminate local analog loopback. while the unit's LLB jumper is set to EN, 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 unit 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 unit's RLB jumper is set to EN, 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 unit 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 unit. 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. Even if those jumpers are set to DIS (Disabled), you can still control loopback testing with these buttons.
Continued on next page.
