Dear Valued Customer:
The conventional fuse in your Model 301-DIV has been replaced with a self-resetting fuse. This new “fuse” is actually a
PTC (positive thermal coefficient) device, which significantly increases resistance when current in the 301-DIV reaches an
unsafe level. This change was made to better protect your 301-DIV and to eliminate the need for you to send the 301-DIV
back to the manufacturer if a fuse is accidentally blown.
If the PTC device has either shut down your equipment or has increased resistance to the point where it affects unit
performance, simply turn off the equipment and allow the PTC device to cool for about 15 to 20 seconds. The 301-DIV
may then be turned back on.
Please note that the most common way in which current is increased to an unsafe level is by improperly biasing the
detector diode. If there is any doubt as to the correct way to bias your particular detector, please contact UDT
Instruments technical support.
UDT Instruments • 8581 Aero Drive • San Diego, CA 92123
Phone (858) 279-8035 Fax (858) 576-9286
