Summary
NMEA 0183 standard GNSS Satellites in View.

Syntax
$GPGSV,<1>,<2>,<3>,<4>,<5>,<6>,<7>,<8>,<9>,<10>,<11>,<12>,<13>,<14>,<15>,<16>,<17>,<18>,
             <19>*hh<CR><LF>

Fields
<1>    Total number of GSV sentences (1 to 3 for internal GPS if WeatherStation)
<2>    Sentence number (1, 2, or 3)
<3>    Total number of satellites in view
<4>    Satellite ID number, 1st SV
<5>    Elevation degrees, 0 to 90, to the nearest degree, 1st SV
<6>    Azimuth, degrees True, to the nearest degree, 1st SV
<7>    SNR (C/No) 00-99 dB-Hz, 1st SV (null field if satellite not tracked)
<8>    Satellite ID number, 2nd SV
<9>    Elevation degrees, 0 to 90, to the nearest degree, 2nd SV
<10>   Azimuth, degrees True, to the nearest degree, 2nd SV
<11>   SNR (C/No) 00-99 dB-Hz, 2nd SV (null field if satellite not tracked)
<12>   Satellite ID number, 3rd SV
<13>   Elevation degrees, 0 to 90, to the nearest degree, 3rd SV
<14>   Azimuth, degrees True, to the nearest degree, 3rd SV
<15>   SNR (C/No) 00-99 dB-Hz, 3rd SV (null field if satellite not tracked)
<16>   Satellite ID number, 4th SV
<17>   Elevation degrees, 0 to 90, to the nearest degree, 4th SV
<18>   Azimuth, degrees True, to the nearest degree, 4th SV
<19>   SNR (C/No) 00-99 dB-Hz, 4th SV (null field if satellite not tracked)

Summary
NMEA 0183 standard GNSS DOP and Active Satellites.

Syntax
$GPGSA,<1>,<2>,<3>,<4>,<5>,<6>,<7>,<8>,<9>,<10>,<11>,<12>,<13>,<14>,<15>,<16>,<17>
              *hh<CR><LF>

Fields
<1>       M = Manual, forced to operate in 2D or 3D. A = Automatic, allowed to automatically switch 2D/3D
<2>       1 = Fix not available, 2 = 2D fix, 3 = 3D fix
<3>       ID numbers of satellite used in solution
<4>       ID numbers of satellite used in solution
<5>       ID numbers of satellite used in solution
<6>       ID numbers of satellite used in solution
<7>       ID numbers of satellite used in solution
<8>       ID numbers of satellite used in solution
<9>       ID numbers of satellite used in solution
<10>     ID numbers of satellite used in solution
<11>     ID numbers of satellite used in solution
<12>     ID numbers of satellite used in solution
<13>     ID numbers of satellite used in solution
<14>     ID numbers of satellite used in solution
<15>     Positional Dilution of Precision (PDOP).  This field is null unless the GPS has a 3D fix.
<16>     Horizontal Dilution of Precision (HDOP). Null unless the GPS has either a 2D fix or a 3D fix.
<17>     Vertical Dilution of Precision (VDOP).  This field is null unless the GPS has a 3D fix.

Summary
NMEA 0183 standard Geographic Position – Latitude/Longitude.

Syntax
$GPGLL,<1>,<2>,<3>,<4>,<5>,<6>,<7>*hh<CR><LF>

Fields
<1>    Latitude, to the nearest .0001 minute
<2>    N if field <1> is North Latitude S if field <1> is South Latitude
<3>    Longitude, to the nearest .0001 minute
<4>    E if field <3> is East Longitude W if field <3> is West Longitude
<5>    UTC of position, in the form hhmmss
<6>    Status:
          A = data valid, V = data invalid
<7>    Mode indicator:
          A = Autonomous mode
          D = Differential mode
          E = Estimated (dead reckoning) mode
          M = Manual input mode
          S = Simulator mode
          N = Data not valid

Summary
NMEA 0183 standard GPS Fix Data.

Syntax
$GPGGA,<1>,<2>,<3>,<4>,<5>,<6>,<7>,<8>,<9>,<10>,<11>,<12>,<13>,<14>*hh<CR><LF>

Fields
<1>    UTC of position, in the form hhmmss
<2>    Latitude, to the nearest .0001 minute
<3>    N if field <2> is North Latitude S if field <2> is South Latitude
<4>    Longitude, to the nearest .0001 minute
<5>    E if field <4> is East Longitude W if field <4> is West Longitude
<6>    GPS quality indicator:
           0 = Fix not available or invalid
           1 = GPS SPS Mode, fix valid
           2 = Differential GPS, SPS Mode, fix valid
           3 = GPS PPS Mode, fix valid
           4 = Real Time Kinematic (RTK)
           5 = Float RTK
           6 = Estimated (dead reckoning) Mode
           7 = Manual Input Mode
           8 = Simulator Mode
<7>    Number of satellites in use, 0-12
<8>    Horizontal dilution of precision (HDOP)
<9>    Altitude relative to mean-sea-level (geoid), meters (to the nearest whole meter)
<10>  M
<11>  Geoidal separation, meters (to the nearest whole meter). 

(Formerly "RS-232") The most common asynchronous serial line standard. EIA-232 is the EIA equivalent of ITU-T V.24, and V.28.
EIA-232 specifies the gender and pin use of connectors, but not their physical type. RS-423 specifies the electrical signals. 25-way D-type connectors are common but often only three wires are connected - one ground (pin 7) and one for data in each direction. The other pins are primarily related to hardware handshaking between sender and receiver and to carrier detection on modems, inoperative circuits, busy conditions etc.
The standard classifies equipment as either Data Communications Equipment (DCE) or Data Terminal Equipment (DTE). DTE receives data on pin 3 and transmits on pin 2 (TD). A DCE EIA-232 interface has a female connector. DCE receives data from DTE on pin 2 (TD) and sends that data out the analog line. Data received from the analog line is sent by the DCE on pin 3(RD).
Originally DCE was a modem and DTE was a computer or terminal. The terminal or computer was connected (via EIA-232) to two modems, which were connected via a telephone line.
The above arrangement allows a computer or terminal to be connected to a modem with a straight-through (2-2, 3-3) cable. It is common, however, to find equipment with the wrong sex connector or with pins two and three reversed, requiring the insertion of a cable or adaptor wired as a gender mender or null modem. Such an adaptor is also required when connecting a computer directly to a terminal or to another computer without the use of modems.
(1999-12-28)

EIA/TIA-422 define a Balanced (differential) interface; specifying a single, unidirectional driver with multiple receivers (up to 32). RS-422 will support Point-to-Point, Multi-Drop circuits, but not Multi-Point [EIA485]. EIA-485 devices may be used in 422 circuits, but EIA-422 may not be used in 485 circuits (because of the lack of an Enable line). EIA422 is the differential "brother" to EIA423. One application note indicated that the combination of cable length (in meters) and data signaling rate (in bps) for RS422 should not exceed 108. The example provided a maximum speed of 200kbps with a maximum cable length of 500 meter [500 x 200,000]. An EIA-422 driver can support up to 10 loads, at 4K W per load.