SLS JT-DO1 User manual

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JT-DO1 User Manual
The JT-DO1 GPS-disciplined IRIG-B timecode generator produces timecode according to the IRIG-
B007, DC level-shift (DCLS) format with BCD time-of-year (ToY), BCD Year, and Straight Binary
Seconds data. Time and Date information is provided by an onboard GPS receiver with an integrated
antenna 1. The IRIG-B output signal is synchronized to the GPS 1 pulse per second (PPS) output.
The JT-DO1 generates IRIG timecode only when the PPS signal is present. In clear-sky conditions,
the JT-DO1 timecode generator exhibits timing accuracy better than 20 ns. For indoor installations,
timing accuracy is better than 500 ns. Device specifications are provided in Table 1.
Table 1: JT-DO1 specifications
Physical
Dimensions 4.62-in x 2.12-in x 1.0-in (L x W x H)
Mounting 0.2-in holes (4x)
Power
Supply Voltage 4.5 V-18 V
Current Consumption 60-160 mA
Environmental
Operating Temperature -20 ° C - +75 ° C
Communication
Serial 115,200 N-8-1
Timing Accuracy
Clear Sky ≤20 ns
Indoors ≤500 ns
1The standard JT-DO1 timecode generator includes an integrated patch antenna. For indoor applications, or other
applications where the device does not have a clear-sky field of view, the JT-DO1 is available with an additional coaxial
input to support the connection of an external GPS antenna.
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Physical
An annotated underside view of the JT-DO1 timecode generator is shown in Figure 1. The JT-DO1
chassis is machined from UV-resistant black Delrin with machined 6061 aluminum front and rear
panels. The footprint of the unit is 4.62-in (L) by 2.12-in (W). The chassis height is 1.0-in. The
chassis is drilled with four 0.2-in mounting holes (two on each flange). The flange mounting holes
are separated by 1.0-in. An additional mounting slot is provided between the mounting holes on
each flange. If the internal patch antenna is specified, the unit should be mounted on a horizontal,
upward-facing surface. If an external antenna is specified, the unit may be mounted in any orientation.
Figure 1: Footprint dimensions of the JT-DO1 timecode generator.
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Connections
Annotated views of the front and rear panels of the JT-DO1 timecode generator are shown in Figure 2
and Figure 3. The front panel provides 50 Ω SMA female connectors for the IRIG-B DCLS output and
the 1 PPS output. In addition, the front panel provides three LED indicators for power (solid red),
GPS lock status (solid green), and PPS (flashing blue). A reset button is accessible through a small
opening in the front panel, suitable for a paperclip or similar probe. The rear panel provides power
and serial connections through keyed, pluggable Phoenix screw terminals. The mating connectors for
both the power and serial connections on the JT-DO1 timecode generator are provided. Power polarity
(+/-) and serial pinout (GND, TX, RX) are engraved on the rear panel. For applications that require
an external GPS antenna, the rear panel also includes an additional SMA bulkhead connector. Note
that Figure 3 shows the JT-D01 timecode generator with the optional external antenna input.
Figure 2: Annotated view of the JT-DO1 timecode generator front panel connections and features.
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Figure 3: Annotated view of the JT-DO1 timecode generator rear panel connections and features.
Environmental
The JT-DO1 timecode generator is designed to be operated in the indoor environment. Operating the
unit unprotected in the outdoor environment will likely result in irreparable damage to the internal
electronics. The acceptable operating temperature range of the JT-DO1 timecode generator is from
-20 ° C to +75 ° C.
Operation
The JT-DO1 is powered from a DC source with acceptable input voltage range from 4.5 V to 18 V
applied to the rear panel screw terminal connector (see Figure 3). On power-up, the device will
immediately begin the process of locking to the satellite constellation. When a GPS lock has been
obtained, the green GPS Lock indicator LED on the front panel will illuminate in green and the PPS
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LED indicator will begin flashing in sync with the PPS output.
The JT-DO1 provides both buffered IRIG-B and PPS outputs from the front panel SMA connectors.
Both outputs can drive a 50 Ω load (nominally 2.75 V into a 50 Ω load and 3.3 V into a high-impedance
load). If both the IRIG-B and PPS outputs are connected to 50 Ω loads, the maximum current
consumption of the device is 160 mA. If the IRIG-B and PPS outputs are connected to high-impedance
loads (or are disconnected), the typical current consumption is 60 mA.
Time, date, and status information are continuously reported over the RS232 serial port, which is
accessible via the three-position screw terminal on the rear panel of the device. The serial port
operates with baud rate of 115,200 bits-per-second, 8 data bits, no parity bit and one stop bit. Note
the serial port will not respond to external commands.
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