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DNT900 - 08/16/10
5 V
L o g i c
D N T 5 0 0
2 . 2 K
4 . 3 K
Figure 3.6.1
3.7 Power-On Reset Requirements
When applying power to the DNT900, the /RESET Pin 39 and the RADIO_TXD Pin 31 must be initially
held low. The /RESET pin must be held low until the power supply voltage reaches 3.3 volts for 100 ms,
and then set high. The RADIO_TXD must be held low an additional 10 ms after the /RESET pin goes
high. RADIO_TXD is weakly pulled down with a 100K ohm resistor to meet the power-on reset require-
ment, unless this line is driven high by an external signal.
3.8 Mounting and Enclosures
DNT900C radio modules are mounted by reflow soldering them to a host circuit board. DNT900P mod-
ules are mounted by plugging their pins into a set of mating connectors on the host circuit board. Refer to
Section 8.3 and/or the DNT900 Data Sheet for DNT900P connector details.
DNT900 enclosures must be made of plastics or other materials with low RF attenuation to avoid com-
promising antenna performance where antennas are internal to the enclosure. Metal enclosures are not
suitable for use with internal antennas as they will block antenna radiation and reception. Outdoor enclo-
sures must be water tight, such as a NEMA 4X enclosure.
3.9 Labeling and Notices
DNT900 FCC Certification - The DNT900 hardware has been certified for operation under FCC Part 15
Rules, Section 15.247. The antenna(s) used for this transmitter must be installed to provide a separation
distance of at least 20 cm from all persons and must not be co-located or operating in conjunction with
any other antenna or transmitter.
DNT900 FCC Notices and Labels - This device complies with Part 15 of the FCC rules. Operation is
subject to the following two conditions: (1) this device may not cause harmful interference, and (2) this
device must accept any interference received, including interference that may cause undesired operation.
A clearly visible label is required on the outside of the user’s (OEM) enclosure stating ”Contains FCC ID:
HSW-DNT900P.”
WARNING: This device operates under Part 15 of the FCC rules. Any modification to this device, not
expressly authorized by RFM, Inc., may void the user’s authority to operate this device.