AN1087

8/13/2019 AN1087

1/3

Net2V4

07/04/2010

RS485 data line limitations

The Net2 data line uses RS485 data signalling. This specifies that the data line is connected to theunits as a series of point-to-point nodes, NOT as a star, ring or multiple line network. The two ends

of the cable must have termination resistors connected across both data pairs and the total length

of any single line must not exceed 1000 metres.

Without termination resistors, reflections of these fast signals will cause data propagation (multiple

signals) resulting in some data corruption. Star and ring layouts do not allow correct termination

and so are not allowed because of these signal reflections.

Extending the data line beyond 1000 metres

No individual data cable can be longer than 1000 metres as this is limited by the drive circuit of the

data converter. By using a repeater we can originate another 1000 metres of data line from any

point. For example, if we require a data line of 1500 metres, a repeater can be placed at any point

within 1000 metres of either end.

The two sections become individual data lines and therefore both must be terminated at each end

of both lines.

This unit has onboard resistors which can be put into circuit byputting the jumper across the 2 pins.

A

B

C

D

SCRN

A

B

C

D

SCRN

Red12vdc

Brown

Orange

Green

Yellow

Blue

Mauve

Black/White

Brown

Yellow

Reader1

Orange

Keypad1

+12v

0v

N.C.

N.O.

Com

N.C.

N.O.

Com

Alarm Output

0v

Contact

0v

Exit

0v

Tamper

PSU

Rx

Tx

Relay1

Relay2

Exit

Contact

Tamper

PSU

OK 5v

12v

Red

Brown

Orange

Green

Yellow

Blue

Mauve

Black/White

Brown

Yellow

Orange

Reader 2Keypad2

Power

Relay1

Relay2

Inputs

Network

CAT5cablecoding

White/Green

Green

White/Orange

Orange

1

2

3

4

Screenorsparecoresfromnetworkcable

CAUTION:for12vd.c.readersonly.

For

correctconnectionofold5vreaders,referto

instructions.

Serialnumber

241821

TestID:012345678901

z-1440

3

24898

00000

4

Termination resistors x2

Resistor jumpers fitted

Greater than 1000 metres


Up to 5 repeaters can be used on a data network. This gives a maximum distance of 6000 metres

for a data line with a repeater placed every 1000 metres down the line

The repeater has input and output ports labelled PC and ACU. The unit should always have the PC

port on the side nearest to the converter.

Although the repeater is a bi-directional unit, the LED indications will be incorrect if this is not done.

AN1087 - How to create multiple data lines and side spurs with a repeater

AN1087 - How to create multiple data lines

and side spurs with a repeater

1

8/13/2019 AN1087

2/3

Net2V4

Spurs and multiple data lines

As a repeater creates a new data line it can be set up to originate a side spur. Wire the repeater

input port as you would an ACU and the output port will then drive a new data line. - see following

diagram.

NOTE: Each individual data line requires a set of resistors at each end. Where a repeater doesnot form the end of a line ( the port has both in and out going data lines ) it does not require

terminating resistors. The 1000 metre limitation will apply to this single line.

Resistor jumpers removed

A

B

C

D

SCRN

A

B

C

D

SCRN

Red12vdc

Brown

Orange

Green

Yellow

Blue

Mauve

Black/White

Brown

Yellow

Reader1

Orange

Keypad1

+12v

0v

N.C.

N.O.

Com

N.C.

N.O.

Com

Alarm Output

0v

Contact

0v

Exit

0v

Tamper

PSU

Rx

Tx

Relay1

Relay2

Exit

Contact

Tamper

PSU

OK 5v

12v

Red

Brown

Orange

Green

Yellow

Blue

Mauve

Black/White

Brown

Yellow

Orange

Reader 2Keypad2

Power

Relay1

Relay2

Inputs

Network

CAT5cablecoding

White/Green

Green

White/Orange

Orange

1

2

3

4



For


instructions.

Serialnumber

241821

TestID:012345678901

z-1440

3

24898

00000

4



Further side spurs can be added to the original data line - for example a single main corridor

with several side corridors or a building staircase with several floors to service.

These side spurs can have their own spurs - for example on a university campus containing

groups of individual buildings. Experience shows that up to 5 repeaters can be used on a single

network without loss of signal quality.

The following examples should help to explain this more fully.



A

B

C

D

SCRN

A

B

C

D

SCRN

A

B

C

D

SCRN

A

B

C

D

SCRN



A

B

C

D

SCRN

A

B

C

D

SCRN


ABCD SCRN

A B C DSCRN

ABCD SCRN

A B C DSCRN



Red12vdc

Brown

Orange

Green

Yellow

Blue

Mauve

Black/White

Brown

Yellow

Reader1

Orange

Keypad1

+12v

0v

N.C.

N.O.

Com

N.C.

N.O.

Com

Alarm Output

0v

Contact

0v

Exit

0v

Tamper

PSU

Rx

Tx

Relay1

Relay2

Exit

Contact

Tamper

PSU

OK 5v

12v

Red

Brown

Orange

Green

Yellow

Blue

Mauve

Black/White

Brown

Yellow

Orange

Reader 2Keypad2

Power

Relay1

Relay2

Inputs

Network

CAT5cablecoding

White/Green

Green

White/Orange

Orange

1

2

3

4



For


instructions.

Serialnumber

241821

TestID:012345678901

z-1440

3

24898

00000

4


AN1087 - How to create multiple data lines and side spurs with a repeater 2

8/13/2019 AN1087

3/3

Net2V4

Star formations

A traditional star formation is not possible as previously explained but the normal limitation of

two data lines ( one line with the PC in the middle ) can be greatly expanded by means of several

repeaters, up to a maximum of 12 lines. However, it is unlikely that this will be the best method

of wiring the data line network as it is being serviced by a single PC port. Multiple serial portssupporting 4 or 5 lines would normally be a far better option.

A

B

C

D

SCRN

A

B

C

D

SCRN

A

B

C

D

SCRN

A

B

C

D

SCRN

A

B

C

D

SCRN

A

B

C

D

SCRN

A

B

C

D

SCRN

A

B

C

D

SCRN






AN1087 - How to create multiple data lines and side spurs with a repeater 3

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