Cisco Systems OL-31454-01 manual Signaling Standards Supported, Distance Limitations

Chapter 2 Preparing for Router Installation

Network Cabling Specifications

Table 2-1	Typical DTE and DCE Devices
Device Type		Gender	Typical Devices
DTE		Male1	Terminal
			PC
DCE		Female2	Modem
			CSU/DSU
			Multiplexer

1.If pins protrude from the base of the connector, the connector is male.

2.If the connector has holes to accept pins, the connector is female.

Signaling Standards Supported

The synchronous serial ports available for the router support the following signaling standards: EIA/TIA-232 (EIA-323). You can order a Cisco DB-25 shielded serial transition cable that has the appropriate connector for the standard you specify. The documentation for the device should indicate the standard used for that device. The router end of the shielded serial transition cable has a DB-25 connector, which connects to the DB-25 port on a serial grid router WAN interface card. The other end of the serial transition cable is available with a connector appropriate for the standard you specify. For a list of the serial cables supported for GRWICs as well as the pinouts, see “Connectors and Cabling for the 8-Port Asynchronous/ Synchronous RS-232 GRWIC” section on page 3-33.

The synchronous serial port can be configured as DTE or DCE, depending on the attached cable.

All serial ports configured as DTE require external clocking from a CSU/DSU or other DCE device.

Distance Limitations

Serial signals can travel a limited distance at any given bit rate; generally, the slower the data rate, the greater the distance. All serial signals are subject to distance limits, beyond which a signal significantly degrades or is completely lost.

Table 2-2lists the recommended maximum speeds and distances for each serial interface type; however, you might get good results at speeds and distances greater than those listed, if you understand the electrical problems that might arise and can compensate for them. For instance, the recommended maximum rate for V.35 is 2 Mb/s, but 4 Mb/s is commonly used.

Table 2-2	Serial Signal Transmission Speeds and Distances
		Distance for		Distance for X.21 and
		EIA/TIA-232		V.35		Distance for USB
Rate (bps)		Feet	Meters	Feet	Meters	Feet	Meters
2400		200	60	4100	1250	16.4	5
4800		100	30	2050	625	16.4	5
9600		50	15	1025	312	16.4	5
19200		25	7.6	513	156	16.4	5
38400		12	3.7	256	78	16.4	5

Cisco 2010 Connected Grid Router Hardware Installation Guide

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