Document No. 485RPTR0501 - pg. 1/3
B&B Electronics January 2001
This product designed and manufactured in USA of domestic and imported parts by
RS-422/485 Line Repeater
With Surge Suppression
Model 485RPTR
Introduction
The 485RPTR can extend RS-485 data lines an additional 4000 feet. The
485RPTR can expand an existing RS-485 system greater than the 32 node
limitation defined by the RS-485 Standard. A typical setup using the 485RPTR as
an RS-485 repeater is shown in Figure 3. The unit has surge suppression on
both sides to dampen any transient voltage spikes.
The 485RPTR uses terminal blocks on each side of the device and supports Transmit Data (A) and (B), Receive Data
(A) and (B), Signal Ground, and Protective Ground. Switch positions are the same for both switches on the 485RPTR
(e.g. switch position 3 on both switches is 9600 baud).
Connection
The 485RPTR can operate in two-wire half-duplex systems, four-wire half-duplex systems, or full-duplex systems (see
Figures 1 and 2). The 485RPTR can also operate as a four-wire to two-wire converter (Figure 2). By connecting one side
of the 485RPTR as a two-wire device and one side as a four-wire device, equipment meant for a point-to-point RS-422
interface can be connected directly to an RS-485 two-wire multi-drop system.
As a good practice, protective ground (Prot.GND) should be tied to a good frame (chassis, green wire, or earth)
ground. The RS-422/485 Application Note explains how to use termination resistance and how to ground RS-422/485
systems. The Application Note is available on B&B's web site or one can be mailed to you free of charge upon request.
Operation
When no data is being transmitted through the 485RPTR, the receivers are enabled on both sides of the device. As
data is received on one side of the 485RPTR, the opposite driver is enabled. When the 485RPTR receives the falling
edge of the last data bit, it waits one character time to disable the driver. This timeout period is factory preset for about
one millisecond to accommodate a baud rate of 9,600 bits per second. The timeout period can be selected with
dipswitches by removing the cover. The preset baud rate dipswitch settings available on the 485RPTR should
accommodate most systems. Alternative timeouts can be achieved by turning the baud rate dipswitches OFF (for
recommended baud rates timeouts see table 2) and placing a specified value through hole resistor (R7 & R26) and/or
through hole capacitor (C2 & C7). Through hole resistor values for time-out periods are given in Table 2.
The 485RPTR is set up at B&B in two-wire mode (switch positions 7 & 8 are ON) at a baud rate of 9600 (switch
position 3 is ON).
Specifications
Data Rates:
Up to 460.8K baud.
Temperature Rating: 0
C to +80
C
Power Requirements: 9 to 14VDC @ 60mA
Dimensions:
3.8"L x 2.4"W x 1.0"H
FCC Approved Class A
Document No. 485RPTR0501 - pg. 2/3
B&B Electronics January 2001
This product designed and manufactured in USA of domestic and imported parts by
Table 2. Typical Setups
Position 7
TX Enable
Position 8
RX Enable
RS-485
2-Wire Mode
(half duplex)
ON ON
RS-485
4-Wire Mode
(full duplex)
ON OFF
RS-422 Mode
(full duplex)
OFF OFF
Table 1. Baud Rate Selection
Position
1
Position
2
Position
3
Position
4
Position
5
Position
6
R7 &
R26
Time
(ms)
1200
OFF OFF OFF OFF OFF OFF 820k
9.02
2400
ON OFF OFF OFF OFF OFF
Not
Used
4.73
4800
OFF ON OFF OFF OFF OFF
Not
Used
2.20
9600
OFF OFF ON OFF OFF OFF
Not
Used
1.10
19200
OFF OFF OFF ON OFF OFF
Not
Used
.62
38400
OFF OFF OFF OFF ON OFF
Not
Used
.29
57600
OFF OFF OFF OFF OFF ON
Not
Used
.17
76800
ON OFF ON ON OFF OFF
Not
Used
.15
115200
ON ON ON OFF OFF OFF
Not
Used
.11
153600
OFF OFF OFF OFF OFF OFF 6.2k
.07
230400
OFF OFF OFF OFF OFF OFF 4.3k
.05
460800
OFF OFF OFF OFF OFF OFF 2k
.02
F ig . 3 4 8 5 R P T R A S A T W O W IR E R S - 4 8 5 R E P E AT E R
S I G . G R O U N D
T X / R X A ( - )
T X / R X B ( + )
H O S T D E V I C E
4 8 5 D E V I C E
S
I
G
.
GR
OU
N
D
TX
/
R
X
B
(
+
)
T
X
/
R
X
A
(-)
U P T O 4 0 0 0 F T. O F C A B L E A N D
2 9 O T H E R R S - 4 8 5 D E V I C E S
4 8 5 D E V I C E
S
I
G.
GR
OU
N
D
U P T O 4 0 0 0 F T. O F C A B L E A N D
3 0 O T H E R R S - 4 8 5 D E V I C E S
4 8 5 R P T R
S I G N A L G N D
P R O T. G N D
D ATA O U T ( A )
D ATA O U T ( B )
S I G . G N D
P R O T. G N D
D ATA IN (A )
D ATA I N ( B )
D ATA O U T ( A )
D AT A O U T ( B )
D ATA IN ( A )
D A TA IN ( B )
T
X
/
R
X
A
(-)
TX
/
R
X
B
(
+
)
+ 1 2 V D C
G N D
G N D
+ 1 2 V D C
R S - 4 8 5 O U T P U T
S IG N A L G N D
D ATA O U T (A ) -
D ATA O U T (B ) +
4 8 5 R P T R
P R O T. G N D
D ATA IN (A ) -
D ATA IN (B ) +
G N D
+ 1 2 V D C
S O L ID B L A C K W IR E
W H IT E M A R K E D W IR E
S IG N A L G N D
T D B (+ )
T D A (-)
R D A ( -)
R D B (+ )
F IG . 1 F O U R W IR E S E T U P
F I G . 2 4 8 5 R P T R A S A F O U R W I R E T O T W O W I R E C O N V E R T E R
T O R S - 4 8 5 N E T W O R K
S I G N A L G R O U N D
D ATA A (- )
D ATA B ( + )
D ATA IN ( A )
S I G . G N D
D ATA IN ( B )
D ATA O U T ( A )
D ATA O U T (B )
P R O T. G N D
T D A ( - )
F O U R W I R E
R S - 4 2 2 D E V I C E
R D B ( + )
T D B ( + )
R D A ( - )
S I G . G N D
D ATA O U T ( A )
S I G N A L G N D
D ATA O U T ( B )
D ATA IN ( A )
D ATA IN ( B )
P R O T. G N D
4 8 5 R P T R
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