Serial Cable Maximum Length

1. Rs232 Serial Cable Maximum Length
2. Serial Cable Maximum Length Calculator
3. Db9 Serial Cable Maximum Length

The RS-232 standard 9600bps port will drive 15 metres of shielded cable. More precisely, an RS-232 line driver will operate against a capacitance of up to 2500 picoFarad with low enough skew to allow a 9600bps signal to be recovered.

If you select a cable with lower capacitance you can drive further distances. For example, ANSI/TIA/EIA-568-A unshielded twisted pair category 5 cable has a maximum capacitiance of 55pF per metre, so this popular 'UTP cat 5' cable can be safely driven up to 45m. Beyond that you should check the cable manufacturers specifications for the actual 'shunt capacitance' (a common figure is 47.5 pF/m, giving a maximum cable length of about 50m). However long runs of unshielded cable will pick up noise easily, as the RS-232 signals are not balanced. Some cable manufacturers offer shielded low capacitance cables which can be driven up to 100m.

1. It is generally accepted that RS-485 can be used with data rates up to 10 Mbit/saor, at lower speeds, distances up to 1,200 m (4,000 ft). As a rule of thumb, the speed in bit/s multiplied by the length in metres should not exceed 108. Thus a 50-metercable should not signal faster than 2 Mbit/s.
2. For a standard shielded cable the Data Rate and corresponding Maximum cable lengths are as follows: 2400 bps – 60m – 200ft 4800 bps – 30m – 100ft 9600 bps – 15m – 50ft.

Supports the Ethernet maximum length of 328 feet (100 meters). Although we do not recommend manufacturing your own serial cables (because of the small size of the pins on the DB-60 serial connector), cable pinouts are provided in the Cisco Modular Access Router. The current maximum length for a serial cable is around 50 meters. Different cables have length limits with the maximum varying.

Similarly, if you select a lower data rate you can drive further distances. Table 11-1 shows the maximum distances over standard shielded cable at differing data rates.

Table 11-1. Data rates and the maximum distances recommended in RS-232

2400

60

4800

30

9600

Rs232 Serial Cable Maximum Length

15

19200

7.6

38400

3.7

56000

Serial Cable Maximum Length Calculator

2.6

Db9 Serial Cable Maximum Length

If you are comfortable in working beyond specifications then you might note that the experience of enterprise network operators has been that structured cabling layout in buildings is limited by the 100m distance limitation of fast ethernet over category 5 cable, not by the practical distances achieved by RS-232 asynchronous signals at 9600bps over category 5 cable.

For longer distances use an RS-232 line driver; these will typically drive up to 2000 meters over category 3 UTP cable. For greater distances consider using fiber optical modems, the global telephony system, the mobile telephony system, satellite or radio.