Furuno Doppler Speedlog DS-510, Installation Manual, Page: 37 / 66

5.3 Remarks on Connection of Other Equipment
30
2. NMEA I/O circuit
1
2
3
4
5
9
10
NC
NC
TXD-H
TXD-C
RXD-H
RXD-C
5V 5V
470
Ω
180
Ω
47
Ω
CIF: ON
NMEA: OFF
J2/J3
SRCN2A16/10S SRCN6A16/10P
CO-0, 2x5P
MAX 25mA
22
Ω
47
Ω
47
Ω
22
Ω
Figure 5-10 NMEA I/O circuit
The maximum allowable current in the NMEA output line is 25 mA and recommended
current is 10 mA. When terminating the line by a photo coupler for current loop
configuration, take suitable means at the signal receive side to limit the current. If, for
example, forward voltage drop in the coupler is 2.2 V;
[4.8 – 2.2 (V)] / [10 (mA)] – 227 (
ȍ ) = 33 ( ȍ )
therefore, insert a 33 ohm resistor in series in the line.