COMSPHERE 3550 Series Data Service Units2-4 July 1999 3550-A2-GB20-40Where to Place the DSUAs mentioned earlier, the DSU must be placed within6 feet of a dedicated grounded ac outlet that is protectedby a circuit breaker.The distance between the DSU and its DTE must bewithin EIA-232-D/V.24 limits, or V.35 limits if operatingthe DSU at speeds greater than 19.2 kbps.• For the EIA-232 connector, the typical maximumdistance is 50 feet at speeds less than or equal to19.2 kbps. If a longer distance is needed, use highquality, low capacitance cable and ensure that theeffective shunt capacitance of the circuit (measuredat the DSU and including the capacitance of thecable and the DTE) does not exceed 2500picofarads, as specified in EIA-232-D.• For the V.35 connector, the maximum distancerecommended between the DSU and the DTE isnominally 1000 feet.Allow 1 to 2 feet of clearance around the DSU foraccess and cable connections during installation.Installing the DSUBefore installing the DSU, label the circuit breaker thatprotects the ac wall outlet, and make sure that it is set toON. Then, proceed with the installation. Procedure1. Place the DSU in its planned location. Make surethe ventilation slots are not blocked.2. At the rear of the DSU (Figure 2-2), insert the actransformer, circular plug into the interfacelabeled POWER.3. Plug the ac transformer’s 3-prong plug into the acwall outlet.CAUTIONOnly use the powertransformer designed for theModel 3550 DSU. Using othertransformers may result inpersonal injury or damage tothe equipment.Figure 2-2. Model 3550 Electrical Connection
