Westermo TD-36 - Manual (Page 33)

33 6618-2202
… Leased Line connection using 2- or 4-wire
Leased Line connections can be set up using 2-wire (or 4-wire in TD-36 485).
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 maximum 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
Leased Line
To make switch setting active the power must be cycled OFF ≥ ON.
S2:1, 2 ON
S2:2 ON Leased line calling
Leased line answering
S2:5 OFF Leased line 2-wire
S1 Sets speed and parity for the RS-232 port.
S4 Decides line-speed. Must be set in direct mode applications.
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 mm² 175 W/km 1,1 dB/km 23 km 27 km
Ø 0,6 mm* ≈ 0,3 mm² 123 W/km 0,9 dB/km 28 km 33 km
Ø 0,7 mm* ≈ 0,4 mm² 93 W/km 0,8 dB/km 31 km 38 km
Ø 0,8 mm ≈ 0,5 mm² 73 W/km 0,7 dB/km 36 km 43 km
Ø 0,9 mm ≈ 0,64 mm² 59 W/km 0,6 dB/km 42 km 50 km
* Frequently used in the local network