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TEST INSTRUMENT SAFETY
(continued from inside front cover)
6. Some equipment with a two-wire ac power cord, including some with polarized power plugs, is the “hot chassis” type. This
includes most recent television receivers and audio equipment. A plastic or wooden cabinet insulates the chassis to protect the
customer. When the cabinet is removed for servicing, a serious shock hazard exists if the chassis is touched. Not only does this
present a dangerous shock hazard, but damage to test instruments or the equipment under test may result from connecting the
ground lead of most test instruments to a “hot chassis”. To test “hot chassis” equipment, always connect an isolation transformer
between the ac outlet and the equipment under test. The B+K Precision Model TR-110 or 1604 Isolation Transformer, or Model
1653 or 1655 AC Power Supply is suitable for most applications. To be on the safe side, treat all two-wire ac equipment as “hot-
chassis” unless you are sure it has an isolated chassis or an earth ground chassis.
7. On test instruments or any equipment with a 3-wire ac power plug, use only a 3-wire outlet. This is a safety feature to keep the
housing or other exposed elements at earth ground.
8. Never work alone. Someone should be nearby to render aid if necessary. Training in CPR (cardio-pulmonary resuscitation) first
aid is highly recommended.
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