Page 2 - Com Corporation
3Com Corporation 350 Campus Drive Marlborough, MA USA 01752-3064 Copyright © 2006-2007, 3Com Corporation. All rights reserved. No part of this documentation may be reproduced in any form or by any means or used to make any derivative work (such as translation, transformation, or adaptation) without ...
Page 3 - ONTENTS
C ONTENTS A BOUT T HIS G UIDE Before You Start 5Conventions 6Related Documentation 6 I NTRODUCING THE S WITCH 4500G F AMILY About the Switch 4500G 7Switch 4500G 24-Port and 48-Port—Front and Rear Panel Detail 8Switch 4500G 24-Port and 48-Port Front Panel LEDs 10Switch 4500G PWR 24-Port and 48-Port —...
Page 5 - Download the latest; and select the “Support and; Before You Start; Release Notes
A BOUT T HIS G UIDE Download the latest software and documentation for your 3Com switch Thank you for purchasing a 3Com Switch 4500G. As part of our commitment to bringing you the most capable and dependable network equipment, 3Com offers free software maintenance updates and documentation updates o...
Page 6 - Conventions; Com Switch 4500G Family Configuration Guide; Table 1; Notice Icons; Icon; Information note
6 A BOUT T HIS G UIDE Conventions Table 1 lists important conventions that are used throughout this guide. Related Documentation In addition to this guide, the Switch 4500G documentation includes the following: ■ 3Com Switch 4500G Family Configuration Guide This guide contains information on the fea...
Page 8 - Summary of Hardware; Figure 1 displays the front panel of the Switch 4500G 24-Port unit.; Figure 1
8 C HAPTER 1: I NTRODUCING THE S WITCH 4500G F AMILY For information about using the software features of the Switch, refer to the “Command Reference Guide” and the “Configuration Guide”. Summary of Hardware Features Table 2 summarizes the hardware features that are supported by the Switch 4500G. Sw...
Page 9 - Switch 4500G 24-Port and 48-Port—Front and Rear Panel Detail; Figure 2 displays the rear panel of the Switch 4500G 24-Port unit.; Figure 2; Figure 3 displays the front panel of the Switch 4500G 48-Port unit.; Figure 3; Figure 4 displays the rear panel of the Switch 4500G 48-Port unit.; Figure 4
Switch 4500G 24-Port and 48-Port—Front and Rear Panel Detail 9 Figure 2 displays the rear panel of the Switch 4500G 24-Port unit. Figure 2 Switch 4500G 24-Port—rear panel Figure 3 displays the front panel of the Switch 4500G 48-Port unit. Figure 3 Switch 4500G 48-Port—front panel Figure 4 displays t...
Page 10 - Table 3
10 C HAPTER 1: I NTRODUCING THE S WITCH 4500G F AMILY Switch 4500G 24-Port and 48-Port Front Panel LEDs The Switch 4500G 24-Port and 48-Port units provide LEDs on the front panel to allow you to monitor the switch. Table 3 describes these LEDs. You can use the mode button on the front panel to switc...
Page 13 - Switch 4500G PWR 24-Port and 48-Port —Front and Rear Panel Detail; Figure 5; Switch 4500G PWR 24-Port Front Unit’s Front Panel; Figure 6; Switch 4500G PWR 24-Port Unit’s Rear Panel
Switch 4500G PWR 24-Port and 48-Port —Front and Rear Panel Detail 13 Switch 4500G PWR 24-Port and 48-Port —Front and Rear Panel Detail Figure 5 displays the front panel of the Switch 4500G PWR 24-Port unit. Figure 5 Switch 4500G PWR 24-Port Front Unit’s Front Panel Figure 6 displays the rear panel o...
Page 14 - Figure 7 displays the Switch 4500G PWR 48-Port unit’s front panel.; Figure 7; Switch 4500G PWR 48-Port Unit’s Front panel; Figure 8 describes the Switch 4500G PWR 48-Port unit’s rear panel.; Figure 8; Switch 4500G PWR 48-Port Unit’s Rear Panel
14 C HAPTER 1: I NTRODUCING THE S WITCH 4500G F AMILY Figure 7 displays the Switch 4500G PWR 48-Port unit’s front panel. Figure 7 Switch 4500G PWR 48-Port Unit’s Front panel Figure 8 describes the Switch 4500G PWR 48-Port unit’s rear panel. Figure 8 Switch 4500G PWR 48-Port Unit’s Rear Panel (1) 10/...
Page 15 - Table 4 describes the; Table 4
Switch 4500G PWR 24-Port and 48-Port Front Panel LEDs 15 Switch 4500G PWR 24-Port and 48-Port Front Panel LEDs Table 4 describes the Switch 4500G PWR 24-Port and PWR 48-Port units’ LEDs. Table 4 Switch 4500G PWR 24-Port and 48-Port Front Panel LEDs LED Label Status Description Mode LED Mode Rate mod...
Page 16 - Unit; Switch 4500G PWR 24-Port and 48-Port Front Panel LEDs; LED
16 C HAPTER 1: I NTRODUCING THE S WITCH 4500G F AMILY 7-segment digitron display Unit POST running Green, blinking The POST ID of the in-process test is displayed. POST failed Red, blinking The POST ID of the failed test blinks. Loading software Green, blinking A light bar rotates clockwise around t...
Page 18 - Table 5 provides the system specifications for the Switch 4500G.; Table 5; System specifications of the Switch 4500G; Item; Weight
18 C HAPTER 1: I NTRODUCING THE S WITCH 4500G F AMILY System Specifications of the Switch 4500G Table 5 provides the system specifications for the Switch 4500G. Table 5 System specifications of the Switch 4500G Item Switch 4500G 24-Port 3CR17761-91 Switch 4500G 48-Port 3CR17762-91 Switch 4500G PWR 2...
Page 19 - OSTRZE
2 I NSTALLING THE S WITCH This section contains information that you need to install and set up your 3Com ® switch. For information on upgrading your switch, refer to the Switch 4500G Release Notes available at www.3com.com. WARNING: Safety Information. Before you install or remove any components fr...
Page 20 - pourrait rendre la garantie nulle.
20 C HAPTER 2: I NSTALLING THE S WITCH ATTENTION : le fait d’ouvrir le commutateur ou d’altérer la vignette de garantie pourrait rendre la garantie nulle. WARNUNG: Öffnen des Switches oder Manipulation des Garantieaufklebers kann das Erlöschen der Garantie zur Folge haben. PRECAUCIÓN: si se abre el ...
Page 21 - Rack-Mounting the Switch; Figure 9; Installing the switch in a 19-inch rack; Mounting the Front; Mount the front bracket as shown in Figure 10 and Figure 11.; Mount the front bracket to the device; Mounting the Rear; Screw
Rack-Mounting the Switch 21 Figure 9 Installing the switch in a 19-inch rack Mounting the Front bracket Mount the front bracket as shown in Figure 10 and Figure 11. Figure 10 Mount the front bracket to the device Figure 11 Mount the front bracket to the mount angel of the rack Mounting the Rear Brac...
Page 22 - Positions for screw mounting on the switch; Follow the steps below to mount the rear bracket:; Installation completed 1; Three positions for screw mounting; Screw 2 is mounted to the switch.
22 C HAPTER 2: I NSTALLING THE S WITCH Figure 12 Positions for screw mounting on the switch Follow the steps below to mount the rear bracket: 1 Use screws to fix the rear bracket to the rear mount angle. 2 Determine the position for screw mounting on the switch according to the position of the mount...
Page 23 - Do not place heavy objects on your switch.; Powering-up the Switch; Use the following sequence of steps to power-up the Switch.; Checking for Correct
Mounting the Switch on a Desktop 23 Figure 14 Installation completed 2 Mounting the Switch on a Desktop In many cases, standard 19-inch racks are not available. Therefore, switches are often placed on a desktop. To place your switch on a desktop, you simply need to: ■ Make sure that the surface is c...
Page 24 - Table 6; The Switch has no ON/OFF switch the only method of connecting or; Color
24 C HAPTER 2: I NSTALLING THE S WITCH Table 6 PWR LED Colors If there is evidence of a problem, see “Solving Problems Indicated by LEDs” on page 52 for a list of suggested solutions. CAUTION: The Switch has no ON/OFF switch; the only method of connecting or disconnecting mains power is by connectin...
Page 25 - Connecting a Redundant Power Supply; When powering any Switch 4500G from an RPS, make sure that the
Connecting a Redundant Power Supply 25 WARNING: When powering any Switch 4500G from an RPS, make sure that the unit is earthed (grounded) by either connecting the power cord to the unit or by connecting the earth terminal on the rear of the unit to a reliable electrical earth (or by connecting both)...
Page 26 - Table 7; Power Availability; Connecting the Switch; Table 8; Switch 4500G Circuit Breaker and Cable Ratings; Make sure to follow the RPS Manufacturers recommendations when; Rectifiers; 2 AWG (solid or stranded cable
26 C HAPTER 2: I NSTALLING THE S WITCH 1500W rectifiers can provide up to 4500W. Hot removal or insertion of a rectifier does not affect the -48V DC output voltage. Table 7 shows an example of the total power available from several 1500W rectifiers. A minimum of two rectifiers are required for each ...
Page 27 - Connecting the Earthing
Connecting a Redundant Power Supply 27 Figure 15 shows how to connect the power supply to the RPS socket in the back of the switch. Use the cable tie supplied with your switch to support the cable in the back of the RPS connector as shown in Figure 15. Figure 15 RPS Connection to the Switch When the...
Page 28 - Reduced Cabling; — a device powered by a PoE switch can take advantage; Console Cable; Console cable
28 C HAPTER 2: I NSTALLING THE S WITCH power required to the device, providing that the total power budget for the switch is not exceeded. A PoE switch combines the functionality of a standard Ethernet switch with a single power supply that can power multiple devices. Using a PoE switch has the foll...
Page 29 - Connecting Console Cable; Pay attention to the mark on the Console port and be sure to plug the; Table 9
Connecting Console Cable 29 When you want to use the terminal to configure the switch, follow these steps to connect a terminal device to your switch using console cables: 1 Plug the DB-9 female connector of the Console cable to the serial port of the PC or terminal where the switch is to be configu...
Page 31 - Command Line Interface
3 S ETTING U P S WITCH M ANAGEMENT To make full use of the features offered by your switch, and to change and monitor the way it works, you have to access the management software that resides on the switch. Managing the switch can help you to improve the efficiency of the switch and therefore the ov...
Page 32 - CLI Management using the Console Port; Refer to “Setting Up Command Line Interface Management” on page 44.; Web Interface Management over the Network; Refer to “Setting Up Web Interface Management” on page 45.
32 C HAPTER 3: S ETTING U P S WITCH M ANAGEMENT Figure 17 CLI Management using the Console Port Figure 18 CLI Management over the Network Refer to “Setting Up Command Line Interface Management” on page 44. There are two main views in the CLI: ■ User View This view is shown when you first connect to ...
Page 33 - Setting Up Your Switch; SNMP Management; SNMP Management over the Network; Refer to “Setting Up SNMP Management V1 or V2” on page 46.
Setting Up Your Switch 33 SNMP Management You can manage a switch using any network management workstation running the Simple Network Management Protocol (SNMP) as shown in Figure 20. For example, you can use the 3Com Network Director software, available from the 3Com website. For information on the...
Page 34 - Initial Switch Setup and Management Flow Diagram; IP Configuration; You do not have a DHCP or BootP server on your network.
34 C HAPTER 3: S ETTING U P S WITCH M ANAGEMENT Figure 21 Initial Switch Setup and Management Flow Diagram CAUTION: To protect your switch from unauthorized access, you must change all three default passwords as soon as possible, even if you do not intend to actively manage your switch. For more inf...
Page 35 - Automatically Configuring the IP Address using DHCP; Your network uses DHCP to allocate IP information.; Preparing to Manage
Setting Up Your Switch 35 For most installations, 3Com recommends that you configure the switch IP information manually. This makes management simpler and more reliable as it is not dependent on a DHCP or BootP server, and eliminates the risk of the IP address changing. To manually enter IP informat...
Page 36 - Connecting to the; You can find pin-out diagrams for the cable in Appendix A on page 55.; Connecting the Workstation to the Switch; Connecting a Workstation to the Switch using the Console Port
36 C HAPTER 3: S ETTING U P S WITCH M ANAGEMENT Manually Configuring IP Information You can manually configure the switch’s IP information by: ■ Connecting a workstation to the switch’s console port using a console cable. You can then manually enter the IP information using the command line interfac...
Page 37 - Manually Configuring IP Information; Setting Up the Switch with IP Information; admin; Enter
Manually Configuring IP Information 37 ■ 19,200 baud (bits per second) ■ 8 data bits ■ no parity ■ 1 stop bit ■ no hardware flow control Refer to the documentation that accompanies the terminal emulation software for more information. 3 Power up the switch. The Power on Self Test (POST) run automati...
Page 38 - User View Login
38 C HAPTER 3: S ETTING U P S WITCH M ANAGEMENT Figure 23 User View Login Starting......*********************************************************** * * * Switch 4500G 48-Port BOOTROM, Version 120 * * * ***********************************************************Copyright (c) 2004-2007 3Com Corporatio...
Page 39 - interface vlan 1; quit
Manually Configuring IP Information 39 3 Enter the system-view command and press Enter . The [S4500G] prompt is displayed. 4 Type interface vlan 1 and press Enter . 5 Enter the IP address and subnet mask for the switch as follows: ip address xxx.xxx.xxx.xxx mmm.mmm.mmm.mmm (where xxx.xxx.xxx.xxx is ...
Page 40 - Connecting to a Front; Connecting a Workstation to the Switch using a Front Panel Port; Do not interconnect the switch to any other unconfigured switch.
40 C HAPTER 3: S ETTING U P S WITCH M ANAGEMENT You can now set up your chosen management method. See “Methods of Managing a Switch” on page 31. If you do not intend to use the command line interface using the console port to manage the switch, you can disconnect the serial cable and close the termi...
Page 41 - Using the Web Interface
Manually Configuring IP Information 41 Setting Up the Switch with IP Information You can now review or change the switch’s IP information. You can do this using the Web interface or the command line interface (CLI) using telnet. Using the Web Interface 1 Power-up the switch. This takes approximately...
Page 42 - User View Login using Telnet
42 C HAPTER 3: S ETTING U P S WITCH M ANAGEMENT Figure 25 User View Login using Telnet 4 Enter the system-view command and Enter. 5 Enter interface vlan 1 and Enter. 6 Enter the IP address and subnet mask for the switch as follows: ip address xxx.xxx.xxx.xxx mmm.mmm.mmm.mmm (where xxx.xxx.xxx.xxx is...
Page 43 - Viewing Automatically Configured IP Information; display ip interface br
Viewing Automatically Configured IP Information 43 Most DHCP and BootP servers allow static IP addresses to be configured so that you know what IP address the switch will be given. Refer to the documentation that accompanies your DHCP or BootP server. If your network does not have a DHCP or BootP se...
Page 44 - User Interface Overview; Check you can communicate with the switch by entering a; ping; command at the; as your user name and press
44 C HAPTER 3: S ETTING U P S WITCH M ANAGEMENT If you do not intend to use the command line interface using the console port to manage the switch, you can logout, disconnect the serial cable and close the terminal emulator software. Setting Up Command Line Interface Management This section describe...
Page 45 - Setting Up Command Line Interface Management using SSH; Prerequisites; A suitable Web browser.; Choosing a Browser; Browser
Setting Up Command Line Interface Management using SSH 45 If the login prompt does not display immediately, press Return a few times until it starts. 6 If you have logged on correctly, the switch you want to manage is displayed as <4500G> , as shown in Figure 23 on page 38. Setting Up Command ...
Page 46 - Web Management Over
46 C HAPTER 3: S ETTING U P S WITCH M ANAGEMENT Web Management Over the Network To manage a switch using the web interface over an IP network: 1 Check that you have the IP protocol correctly installed on your management workstation. You can check this by trying to browse the World Wide Web. If you c...
Page 47 - Default Users and Passwords; can do this using the command line interface; system management snmp; command. Refer to the command line interface section of the; password simple xxxxxxxx; xxxxxxxx; Save the configuration in the User View.; Access Level
Default Users and Passwords 47 can do this using the command line interface system management snmp community command. Refer to the command line interface section of the “SuperStack 4 Switch Command Reference Guide” for more information. SNMP V3 is on as default. All commands are in snmp menu in Syst...
Page 49 - 500G Command Reference Guide
4 P ROBLEM S OLVING This chapter helps you to diagnose and solve problems you may have with the operation of your switch. There is also an explanation of IP addressing and upgrading software. The topics covered are: ■ Solving Problems Indicated by LEDs ■ Solving Hardware Problems ■ Solving Communica...
Page 50 - The PWR LED does not light
50 C HAPTER 4: P ROBLEM S OLVING Solving Problems Indicated by LEDs If the LEDs on the switch indicate a problem, refer to the list of suggested solutions below. The PWR LED does not light Check that the power cable is firmly connected to the switch and to the supply outlet. If the connection is sec...
Page 51 - Solving Hardware Problems; display logbuffer
Solving Hardware Problems 51 Solving Hardware Problems In the rare event of your switch unit experiencing a hardware failure, refer to the list of suggested solutions below. A fan failure warning message is received Your switch has a fan monitoring system that will generate fan failure warning messa...
Page 52 - Error message indicating that the SFP transceiver is invalid; The switch IP address and Management VLAN ID has been configured.; IP Addressing; where; How do you obtain a registered IP Address?; World Wide Web site:
52 C HAPTER 4: P ROBLEM S OLVING Error message indicating that the SFP transceiver is invalid The switch has identified that the SFP does not meet the minimum requirements for the switch and has disabled the port. To correct this problem, completely remove the SFP and replace it with a 3Com approved...
Page 53 - Solving Fabric Formation Problems; Power off all units in the fabric.
Solving Fabric Formation Problems 53 another device on your network. 3Com suggests you use addresses in the range 192.168.0.0 to 192.168.255.255 with a subnet mask of 255.255.255.0. These suggested IP addresses are part of a group of IP addresses that have been set aside specially for use ‘in house’...
Page 55 - Null Modem Cable
A P IN - OUTS Null Modem Cable RJ-45 to RS-232 25-pin PC-AT Serial Cable RJ-45 to 9-pin Screen TxDRxDGroundRTSCTSDSRDCDDTR Screen RxDTxDGroundRTSDTRCTSDSRDCD Shell 32578614 1 327420568 Switch 5500Cable connector: RJ-45 female PC/TerminalCable connector: 25-pin male/female only required if screen alw...
Page 56 - Modem Cable; Screen; Pin Number; Ports configured as MDI
56 A PPENDIX A: P IN - OUTS Modem Cable RJ-45 to RS-232 25-pin Ethernet Port RJ-45 Pin Assignments 10/100 and 1000BASE-T RJ-45 connections. Table 10 Pin assignments Screen TxDRxDRTSCTSDSRGroundDCDDTR Screen TxDRxDRTSCTSDSRGroundDCDDTR Shell 32786514 1234567820 Switch 5500Cable connector: RJ-45 femal...
Page 57 - Ethernet Port RJ-45 Pin Assignments; Ports configured as MDIX
Ethernet Port RJ-45 Pin Assignments 57 Table 11 Pin assignments Pin Number 10/100 1000 Ports configured as MDIX 1 Receive Data + Bidirectional Data B+ 2 Receive Data − Bidirectional Data B − 3 Transmit Data + Bidirectional Data A+ 4 Not assigned Bidirectional Data A − 5 Not assigned Bidirectional Da...
Page 59 - Physical Dimensions
B T ECHNICAL S PECIFICATIONS Switch 4500G 24-Port Physical Dimensions Height: 44 mm (1.7 in.) x Width: 440 mm (17.3 in.) x Depth: 274 mm (10.8 in.) Weight: 4.4kg (9.72 Ibs) Environmental Requirements Operating Temperature 0 ° to 40 °C (32 ° to 104 °F) Storage Temperature − 10 ° to +70 °C (14 ° to 15...
Page 63 - Grounding Lead; Safety Requirements; UL VW-1 and CSA FT1 Vertical Flame Test; Voltage Rating
Grounding Lead 63 Grounding Lead Safety Requirements The Grounding Cable (in PWR Units only) shall comply with the following safety standards: UL Subject 758, UL 1581 and CSA C22.2 No. 210 UL VW-1 and CSA FT1 Vertical Flame Test Voltage Rating 600V AWG 18 Insulation Thickness 0.4mm Insulation Colour...
Page 65 - Com Knowledgebase —; Helps you to troubleshoot 3Com
C O BTAINING S UPPORT FOR Y OUR 3C OM P RODUCTS 3Com offers product registration, case management, and repair services through eSupport.3com.com . You must have a user name and password to access these services, which are described in this appendix. Register Your Product to Gain Service Benefits To ...
Page 66 - Contact Us; Telephone Technical
66 A PPENDIX C: O BTAINING S UPPORT FOR Y OUR 3C OM P RODUCTS success of your networking projects. For more information on 3Com Extended Warranty and Professional Services, see: http://www.3com.com/ Contact your authorized 3Com reseller or 3Com for additional product and support information. See the...
Page 67 - Product model name, part number, and serial number; Country
Contact Us 67 When you contact 3Com for assistance, please have the following information ready: ■ Product model name, part number, and serial number ■ A list of system hardware and software, including revision level ■ Diagnostic error messages ■ Details about recent configuration changes, if applic...
Page 69 - Com Network Supervisor
D 3C OM N ETWORK M ANAGEMENT 3Com has a range of network management applications to address networks of all sizes and complexity, from small and medium businesses through large enterprises. The applications include: ■ 3Com Network Supervisor ■ 3Com Network Director ■ 3Com Network Access Manager ■ 3C...
Page 70 - monitoring and
70 A PPENDIX D: 3C OM N ETWORK M ANAGEMENT 3Com Network Director 3Com Network Director (3ND) is a standalone application that allows you to carry out key management and administrative tasks on midsize networks. By using 3ND you can discover, map, and monitor all your 3Com devices on the network. It ...
Page 71 - Com Enterprise Management Suite; Customize scheduled bulk operations
3Com Enterprise Management Suite 71 3Com Enterprise Management Suite 3Com Enterprise Management Suite (EMS) delivers comprehensive management that is flexible and scalable enough to meet the needs of the largest enterprises and advanced networks. This solution provides particularly powerful configur...
Page 73 - Important Safety Information
E R EDUNDANT P OWER S UPPLY S AFETY I NFORMATION Important Safety Information WARNING: This device has more than one power input. Disconnect all power inputs to power off this device. WARNING: The installation of the Redundant Power Supply (RPS) should only be carried out by properly trained and qua...
Page 74 - L’information de Sécurité Importante
74 A PPENDIX E: R EDUNDANT P OWER S UPPLY S AFETY I NFORMATION WARNING: Ensure that the circuit breaker in the RPS is in the open (off) position when connecting the RPS cable and connector to the Switch. WARNING: Do not use a standard 'positive-earthed' -48V redundant power system suitable for use w...
Page 75 - Wichtige Sicherheitsinformationen
Wichtige Sicherheitsinformationen 75 AVERTISSEMENT: Assurez-vous que le disjoncteur du RPS est ouvert (off) lors du branchement du câble au RPS. AVERTISSEMENT: Assurez-vous de brancher la borne positive du commutateur à la borne positive (commune) du RPS, et la borne négative du commutateur à la bor...
Page 76 - Información de Seguridad Importante
76 A PPENDIX E: R EDUNDANT P OWER S UPPLY S AFETY I NFORMATION VORSICHT: Diese Anleitungen müssen im Zusammenhang mit den Eigenschaften des Gleichstrom-Versorgungseingangs des Switch 4210 gelesen werden, die in Anhang C, "Technische Daten", aufgeführt sind. VORSICHT: Beim Anschließen des Kab...
Page 78 - Importanti Informazioni di Sicurezza; AVVERTENZA
78 A PPENDIX E: R EDUNDANT P OWER S UPPLY S AFETY I NFORMATION Importanti Informazioni di Sicurezza AVVERTENZA: Il dispositivo presenta più punti di alimentazione. Per spegnere il dispositivo, scollegare tutti i punti di alimentazione. AVVERTENZA: le operazioni di installazione dell'RPS (Redundant P...
Page 79 - Wa¿ne informacje o zabezpieczeniach; Wa
Wa¿ne informacje o zabezpieczeniach 79 standard con 'messa a terra positiva' a -48 V normalmente usati con gli apparecchi di telecomunicazione. Per soddisfare lo standard IEEE 802.3af (PoE), l'uscita a -48V deve essere isolata da terra e soddisfare i requisiti d'isolamento per quello standard. Wa ż ...
Page 81 - Regulatory Notices; FCC Statement; ICES Statement
Regulatory Notices 81 Regulatory Notices FCC Statement This equipment has been tested and found to comply with the limits for a Class A digital device, pursuant to part 15 of the FCC rules. These limits are designed to provide reasonable protection against harmful interference when the equipment is ...