… Leased line connection using 2- or 4-wire
Leased line connections can be set up using either 2- or 4-wire.When renting a 4-wire
line from a telephone company one pair of cables for transmission and one pair for
reception are usually provided.
The maximum transmission distance depends on the attenuation of the line. The maxi-
mum value is theoretically 30 dBm. To have a good error rate it is recommended to keep
the attenuation under 25 dB. When renting lines from a telephone company a longer
transmission distance is normally possible as the signals are probably transmitted over
PCM-lines, i.e. fibre optic or other media with low attenuation.
To set the modem for leased line applications use the dip switches.
Configure the units
S2:1, 2 ON
S2:2 ON
Leased line calling
Leased line answering
S2:5 OFF Leased line 2-wire
S2:5 ON Leased line 4-wire
S1 Sets speed and parity for the RS-232 port.
S3 Decides line-speed. Must be set in direct mode applications.
To make switch setting active the power must be cycled OFF -> ON.
Leased Line
Resistance, attunation and distance for different wires
Tele Cable Area Resistance for
double cable
Attunation Recommended
Max distance
(25 dB)
Max Distance
(30 dB)
Ø 0,5 mm* ≈ 0,2 mm
2
175 W/km 1,1 dB/km 23 km 27 km
Ø 0,6 mm* ≈ 0,3 mm
2
123 W/km 0,9 dB/km 28 km 33 km
Ø 0,7 mm* ≈ 0,4 mm
2
93 W/km 0,8 dB/km 31 km 38 km
Ø 0,8 mm ≈ 0,5 mm
2
73 W/km 0,7 dB/km 36 km 43 km
Ø 0,9 mm ≈ 0,64 mm
2
59 W/km 0,6 dB/km 42 km 50 km
* Frequently used in the local network
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