COBS SMART User manual

1 T100361E_RD_COBS SMART System Guide
SMART System Guide
Installation & Configuration
Network Deployment
Operation & Management
Technical Reference Document
©May-2017 COBS AB, Sweden

2 T100361E_RD_COBS SMART System Guide
Trademarks
COBS and the combinations of its logo thereof are trademarks of COBS AB, Sweden.
Other product names used in this publication are for identification purposes and maybe the trademarks of their respective
companies.
Disclaimer
The contents of this document are provided in connection with COBS products. COBS makes no representations with respect to
completeness or accuracy of the contents of this publication and reserves the right to make changes to product descriptions, usage,
etc., at any time without notice. No license, whether express, implied, to any intellectual property rights are granted by this
publication
Confidentiality
This document should be regarded as confidential, unauthorized copying is not allowed
© May-2017 COBS AB, Sweden, All rights reserved
http://www.cobs.se

3 T100361E_RD_COBS SMART System Guide
Contents
SMART System Guide ........................................................................................................................................ 1
Contents ............................................................................................................................................................ 3
1About This Document................................................................................................................................ 5
1.1 Audience.................................................................................................................................................. 5
1.2 When Should I Read This Guide .............................................................................................................. 5
1.3 Important Assumptions........................................................................................................................... 5
1.4 Abbreviations........................................................................................................................................... 5
2Introduction –System Overview ............................................................................................................... 6
2.1 Hardware Setup....................................................................................................................................... 6
2.2 Components of SMART System............................................................................................................... 6
2.3 Wireless Bands ........................................................................................................................................ 7
2.4 System Capacity (in Summary) ................................................................................................................ 7
2.5 Advantages of SMART System................................................................................................................. 8
3Installation of SMART AP........................................................................................................................... 9
3.1 Package –Contents/Damage Inspection................................................................................................. 9
3.2 SMART AP Mechanics.............................................................................................................................. 9
3.3 SMART AP Base Unit –Reset feature .................................................................................................... 10
3.4 Installing the SMART AP (Base Station)................................................................................................. 10
3.5 Login to base stations with your browser ............................................................................................. 11
4Making Handset Ready............................................................................................................................ 13
4.1 Package –Contents/Damage Inspection............................................................................................... 13
4.2 Before Using the Phone......................................................................................................................... 13
4.3 Using the Handset ................................................................................................................................. 15
5SMART System Administration Interface ................................................................................................ 16
5.1 Web navigation...................................................................................................................................... 16
5.2 Home/Status.......................................................................................................................................... 18
5.3 Extensions.............................................................................................................................................. 19
5.4 Servers ................................................................................................................................................... 22
5.5 Network ................................................................................................................................................. 27
5.6 Management Settings Definitions ......................................................................................................... 31
5.7 Firmware Update Definitions ................................................................................................................ 34
5.8 Time Server............................................................................................................................................ 34
5.9 Country .................................................................................................................................................. 36

4 T100361E_RD_COBS SMART System Guide
5.10 Security ................................................................................................................................................ 37
5.11 Central Directory and LDAP ................................................................................................................. 39
5.12 Multi-cell Parameter Definitions ......................................................................................................... 42
5.13 Repeaters (not supported) .................................................................................................................. 48
5.14 Alarm (Currently not used).................................................................................................................. 50
5.15 Statistics............................................................................................................................................... 50
5.16 Settings –Configuration File Setup ..................................................................................................... 54
5.17 Sys log .................................................................................................................................................. 54
5.18 SIP Logs ................................................................................................................................................ 54
6Setting up a Multi-cell system, best practice .......................................................................................... 55
6.1 Adding Base stations ............................................................................................................................. 55
6.2 Synchronizing the Base stations ............................................................................................................ 59
6.3 Summary of Procedure –Creating a Chain............................................................................................ 61
7Registration Management - Handset ...................................................................................................... 61
7.1 Register a user to the system ................................................................................................................ 61
8Base station Firmware Upgrade Procedure ............................................................................................ 64
8.1 Network Dimensioning.......................................................................................................................... 64
8.2 TFTP Configuration ................................................................................................................................ 64
8.3 Create Firmware Directories ................................................................................................................. 65
8.4 Base Station(s) Firmware Upgrade........................................................................................................ 65
9Revision history ....................................................................................................................................... 67

5 T100361E_RD_COBS SMART System Guide
1 About This Document
This document describes the configuration, customization, management, operation, maintenance and
troubleshooting of the SMART System (SMART AP, SMART1 handset).
1.1 Audience
Who should read this guide? First, this guide is intended for networking professionals responsible for
designing and implementing COBS SMART System a wireless enterprise voice and messaging network.
Second, network administrators and IT support personnel that need to install, configure, maintain and
monitor elements in a “live” SMART System network will find this document helpful. Furthermore, anyone
who wishes to gain knowledge on fundamental features in the system can also benefit from this material.
1.2 When Should I Read This Guide
Read this guide before you install the core network devices of SMART System and when you are ready to
setup or configure SIP server, NAT aware router, advanced VLAN settings, base stations, CMS, SMART
Manager and multi cell setup.
This manual will enable you to set up components in your network to communicate with each other and
also deploy a fully functionally SMART System.
1.3 Important Assumptions
This document was written with the following assumptions in mind:
1) You have understanding of network deployment in general
2) You have working knowledge of basic TCP/IP/SIP protocols, Network Address Translation, etc...
3) A proper site survey has been performed, and the administrator have access to these plans and
documentation.
4) You are familiar with components such as SMART Manager, CMS and SIP pbx systems in general.
1.4 Abbreviations
For the purpose of this document, the following abbreviations hold:
DHCP: Dynamic Host Configuration Protocol
DNS: Domain Name Server
HTTP(S): Hyper Text Transfer Protocol (Secure)
(T)FTP: (Trivial) File Transfer Protocol
IOS: Internetworking Operating System
PCMA: A-law Pulse Code Modulation
PCMU: mu-law Pulse Code Modulation
PoE: Power over Ethernet
RTP: Real-time Transport Protocol
RPORT: Response Port (Refer to RFC3581 for details)
SIP: Session Initiation Protocol
SME: Small and Medium scale Enterprise
VLAN: Virtual Local Access Network
TOS: Type of Service (policy based routing)
URL: Uniform Resource Locator
UA: User Agent

6 T100361E_RD_COBS SMART System Guide
2 Introduction – System Overview
In a typical telephony and messaging system, the network setup is the interconnection between Base-
stations, routers, repeaters, portable parts, etc. The back-bone of the network depends on the deployment
scenario but a typical Ethernet network is used. The system has centralized monitoring and maintenance.
The system is easy to scale up and supports from 1 to 256 (512) bases in the same network. Further is it
able to support up to 1000 registered handsets. The SMART System setup is illustrated below. Based on PoE
interface each base station is easy to install without additional wires other than the from the LAN cable.
The following figure gives a graphical overview of the architecture of the SMART System:
2.1 Hardware Setup
SMART network hardware setup can deployed as follows:
Base-station(s) are connected via Layer 3 and/or VLAN Aware Router depending on the deployment
requirements. The Layer 3 router implements the switching function.
The base-stations are typically mounted on walls so that each base-station is separated from each other by
up to 50m indoor
1
(300m outdoor). Radio coverage can be extended using repeaters that are installed with
same distance to base-station(s).
The base-station antenna mechanism is based on space diversity feature which improves coverage. The
base-stations uses complete DECT MAC protocol layer and IP media stream audio encoding feature to
provide up to 10 simultaneous calls.
2.2 Components of SMART System
COBS SMART System is made up of (but not limited to) the following components:
•At least one SMART Base Station is connected over an IP network and using DECT as air-core interface.
•COBS SMART1 wireless Handset.
•A WiFi access point
1
Measured with European DECT radio and depends on local building layout and material

7 T100361E_RD_COBS SMART System Guide
•COBS SMART Configuration Interface; is a management interface for SME VoIP Wireless Solution. It
runs on all SMART AP base stations. Each Base station has its own unique settings.
2.2.1 COBS Base Stations
The Base Station converts IP protocol to DECT protocol and transmits the traffic to and from the end-nodes
(i.e. wireless handsets) over a channel. It has 12 available channels.
In a multi-cell setup, each base station has:
•8 channels have associated DSP resources for media streams.
•The remaining 4 channels are reserved for control signalling between IP Base Stations and the SIP/DECT
end nodes (or phones).
Base Stations are grouped into clusters. Within each Cluster, Base Stations are synchronized to enable a
seamless handover when a user moves from one base station coverage to another. For synchronization
purposes, it is not necessary for Base Stations to communicate directly with each other in the system. E.g. a
Base Station may only need to communicate with the next in the chain. It is advisable for a Base Station to
identify more than one Base Station to guarantee synchronization in the situation that one of the Base
Stations fails.
The 4 control signalling channels are used to carry bearer signals that enable a handset to initiate a
handover process.
2.2.2 SMART System Administration interface
The SMART System Configuration Interface is a web based administration page used for configuration and
programming of the base station and relevant network end-nodes. E.g. handsets can be registered or de-
registered from the system using this interface.
The configuration interface can be used as a setup tool for software or firmware download to base stations
and handsets. Further, it is used to check relevant system logs that can be useful to administrator. These
logs can be used to troubleshoot the system when the system faces unforeseen operational issues.
2.2.3 COBS Wireless Handset
The handset SMART1 is an Android based, lightweight, ergonomically and portable unit compatible with
Wideband Audio (G.722), DECT, GAP standard, CAT-iQ audio compliant.
The handset includes touch display with graphical user interface. It can also provide the subscriber with
most of the features available for a wired phone, in addition to its roaming and handover capabilities. Refer
to the relevant handset manuals for full details handset features.
2.3 Wireless Bands
The bands supported in the SMART System are summarized as follows:
Frequency bands: 1880 –1930 MHz (DECT)
1880 –1900 MHz (10 frequencies) Europe/ETSI
1910 –1930 MHz (10 frequencies) LATAM
1920 –1930 MHz (5 carriers) US
2.4 System Capacity (in Summary)
SME network capacity of relevant components can be summarised as follows:
Description
Capacity
Min ## of Bases Single Cell Setup
1
Max ## of Bases in Multi-cell Setup
256
Max ## of Users (SIP registrations) per Base
30
Max ## of Users per SMART System
Currently limited to 1000

8 T100361E_RD_COBS SMART System Guide
Multi-cell Setup: Max ## of Synchronisation levels
24
Single Cell Setup: Max ## Simultaneous Calls
10 per Base station
Multi-cell Setup: Max ## of Calls
8 per Base station
Total Max ## Simultaneous Calls (Multi-cell Setup)
Limited to 1000
Quick Definitions
Single Cell Setup: Telephony network composed of one base station
Multi-cell Setup: Telephony network that consists of more than one base station
Synchronisation Level: Is the air core interface between two base stations.
2.5 Advantages of SMART System
They include (but not limited to):
1. Simplicity. Integrating functionalities leads to reduced maintenance and troubleshooting, and significant
cost reductions.
2. Flexibility. Single network architecture can be employed and managed. Furthermore, the architecture is
amenable to different deployment scenarios, including Isolated buildings for in-building coverage, location
with co-located partners, and large to medium scale enterprises deployment for wide coverage.
3. Scalability. SMART network architecture can easily be scaled to the required size depending on customer
requirement.
4. Performance. The integration of different network functionalities leads to the collapse of the protocol
stack in a single network element and thereby eliminates transmission delays between network elements
and reduces the call setup time and packet fragmentation and aggregation delays.

9 T100361E_RD_COBS SMART System Guide
3 Installation of SMART AP
After planning the network, next is to determine the proper places or location the relevant base stations
will be installed. Therefore, we briefly describe the how to install the base station in this chapter.
3.1 Package –Contents/Damage Inspection
Before Package Is Opened:
Examine the shipping package for evidence of physical damage or mishandling prior to opening. If there is a
proof of mishandling prior to opening, you must report it to the relevant support centre of the regional
representative or operator.
Contents of Package:
Make sure all relevant components are available in the package before proceeding to the next step.
Every shipped base unit package/box contains the following items:
2 x mounting screws and 2 x Anchors
1 x Plastic mounting fixture
SMART AP (Base station)
Damage Inspection:
The following are the recommended procedure for you to use for inspection:
1. Examine all relevant components for damage.
2. Make a “defective on arrival – DOA” report or RMA to the operator. Do not move the shipping
carton until it has been examined by the operator. If possible send pictures of the damage. The
operator/regional representative will initiate the necessary procedure to process this RMA. They
will guide the network administrator on how to return the damaged package if necessary.
3. If no damage is found then unwrap all the components and dispose of empty package/carton(s) in
accordance with country specific environmental regulations.
3.2 SMART AP Mechanics
The base station front end shows an LED indicator that signals different functional states of the base unit
and occasionally of the overall network. The indicator is off when the base unit is not powered.

10 T100361E_RD_COBS SMART System Guide
The table below summarises the various LED states:
LED State
State
Unlit
No power in unit
Unlit/Solid red
Error condition
Blinking green
Initialisation
Solid red
Factory reset warning or long press in BS reset button
Blinking red
Factory setting in progress
Solid green
Ethernet connection available (Normal operation)
Blinking red
Ethernet connect not available OR handset de/registration failed
Solid red
Critical error (can only be identified by COBS Engineers). Symptoms
include no system/SIP debug logs are logged, etc.
Orange
Press reset button of base station.
Blinking orange
No IP address received
3.3 SMART AP Base Unit –Reset feature
It is possible to restart or reset the base station unit by pressing a “hidden” reset button on the bottom part
of the SMART AP. Alternatively, it can be reset from the SMART System Configuration Interface.
3.4 Installing the SMART AP (Base Station)
First determine the best location that will provide an optimal coverage taking account the construction of
the building, architecture and choice of building materials.
Next, mount the Base Station on a wall to cover range between 50 –300 meters (i.e. 164 to 984 feet),
depending whether it’s an indoor or outdoor installation.
3.4.1 Mounting the Base Stations
We recommend the base station be mounted an angle other than vertical on both concrete/wood/plaster
pillars and walls for optimal radio coverage. Avoid mounting the base units upside down as it significantly
reduces radio coverage.
Mount the base unit as high as possible to clear all nearby objects (e.g. office cubicles and cabinets, etc.).
Avoid all contacts with any high voltage lines.

11 T100361E_RD_COBS SMART System Guide
3.5 Login to base stations with your browser
STEP 1 Connect the Base station to a private network via standard Ethernet cable (CAT-5).
STEP 2 Find the base stations IP-address through either the DHCP server or a scanner application.
By default the base uses a DHCP assigned IP address.
STEP 3 On the Login page, enter your authenticating credentials (i.e. username and password).
By default the username and password is admin. Click OK button.

12 T100361E_RD_COBS SMART System Guide
STEP 4 Once you have authenticated, the browser will display front end of the SMART System
Configuration Interface. The front end will show relevant information of the base station.

13 T100361E_RD_COBS SMART System Guide
4 Making Handset Ready
In this chapter we briefly describe how to prepare the handset for use, install, insert and charge new
batteries. Please refer to an accompanying Handset User Guide for more information of the features
available in the Handset.
4.1 Package –Contents/Damage Inspection
Before Package Is Opened:
Examine the shipping package for evidence of physical damage or mishandling prior to opening. If there is a
proof of mishandling prior to opening, you must report it to the relevant support centre of the regional
representative or operator.
Contents of Package:
Make sure all relevant components are available in the package before proceeding to the next step.
Every shipped handset package/box contains the following items:
1 x Handset
1 x Battery
1 x Flush rear part (mounted)
1 x Belt clip
Damage Inspection:
The following are the recommended procedure for you to use for inspection:
1. Examine all relevant components for damage.
2. Make a “defective on arrival – DOA” report or RMA to the operator. Do not move the shipping
carton until it has been examined by the operator. The operator/regional representative will
initiate the necessary procedure to process this RMA. They will guide the network administrator on
how to return the damaged package if necessary.
3. If no damage is found then unwrap all the components and dispose of empty package/carton(s) in
accordance with country specific environmental regulations.
4.2 Before Using the Phone
Here are the pre-cautions users should read before using the Handset:
Installing the Battery
1. Never dispose battery in fires, otherwise it will explode.

14 T100361E_RD_COBS SMART System Guide
2. Never replace the batteries in potentially explosive environments, e.g. close to inflammable liquids/
gases.
3. ONLY use approved batteries and chargers from the vendor or operator.
4. Do not disassemble, customise or short circuit the battery
Using the Charger
Each handset is charged through the use of a handset charger. The charger is a compact desktop unit
designed to charge and automatically maintain the correct battery charge levels and voltage.
The charger Handset is powered by AC supply from 110-240VAC that supplies 5.5VDC at 600mA.
When charging the battery for the first time, it is necessary to leave the handset in the charger for at least
10 hours before the battery is fully charged and the handset ready for use.
Handset in the Charger
For correct charging, ensure that the room temperature is between 0°C and 25°C/32°F and 77°F. Do not
place the handset in direct sunlight. The battery has a built-in heat sensor which will stop charging if the
battery temperature is too high.
The handset will always turn on once it is placed in the charger.
Open Back Cover
1. Unlock the battery LID and lift up the back cover.
2. Remove Back Cover from Handset
Handset IPEI Number
The IPEI number of each handset is found either on a label, which is placed behind the battery, or on the
packaging label. First, lift off handset back cover and lift the battery and read the serial number.
The IPEI number is needed to enable service to the handset. It must be programmed into the system
database via the SMART System Configuration interface.

15 T100361E_RD_COBS SMART System Guide
Replace Battery
Remove Back Cover from Handset. Remove the old battery and replace with a new one.
4.3 Using the Handset
Please refer handset manual for detailed description of how to use the handset features [1].

16 T100361E_RD_COBS SMART System Guide
5 SMART System Administration Interface
The SMART System Administration Interface is also known as SMART System Configuration. It is the main
interface through which the system is managed, configured and debugged.
The SMART System Configuration Interface is an in-built HTTP Web Server service residing in each base
station. This interface is a user friendly interface and easy to handle even to a first time user.
Note: Enabling secure web is not possible. For secure configuration use secure provisioning.
This chapter seeks to define various variables/parameters available for configuration in the network.
5.1 Web navigation
We describe the left menu in the front end of the SMART System Administration Interface.
Feature
Description
Home/Status
This is the front end of the Base station’s HTTP web interface. This page shows the
summary of current operating condition and settings of the Base station and
Handset(s).
Extensions
Administration of extensions and handsets in the system
Servers
On this page the user can define which SIP/NAT server the network should connect
to.
Network
Typically the user configures the Network settings from here.
NAT provisioning: allows configuration of features for resolving of the NAT –
Network Address Translation. These features enable interoperability with most
types of routers.

17 T100361E_RD_COBS SMART System Guide
DHCP: allows changes in protocol for getting a dynamic IP address.
Virtual LAN: specifies the Virtual LAN ID and the User priority.
IP Mode: specifies using dynamic (DHCP) or static IP address for your SME network.
IP address: if using DHCP leave it empty. Only write in, when you use static IP
address.
Subnet mask: if using DHCP, leave it empty. Only write in, when you use static IP
address.
DNS server: specify if using DHCP, leave it empty. Only write in the DNS server
address of your Internet service provider, when you use static IP address. (DNS =
Dynamic Name Server)
Default gateway: if using DHCP, leave it empty. Write in the IP address of your
router, when you use static IP address.
Management
Defines the Configuration server address, Management transfer protocol, sizes of
logs/traces that should be catalogued in the system, CMS messaging server
interface.
Firmware
Update
Remote firmware updates (HTTP(s)/TFTP) settings of Base stations and handsets.
Time
Here the user can configure the Time server. It should be used as time server in
relevant country for exact time. The time servers have to deliver the time to
conform to the Network Time Protocol (NTP). Handsets are synchronised to this
time. Base units synchronise to the master using the Time server.
Country
Specifying the country/territory where the SMART System network is located
ensures that your phone connection functions properly.
Note: The base language and country setting are independent of each other.
Security
The users can administrate certificates and create account credentials with which
they can log in or log out of the embedded HTTP web server.
Central
Directory
Interface to common directory load of up to 3000 entries using *csv format or
configuration of LDAP directory.
Note: LDAP and central directory cannot operate at the same time.
Multi cell
Specify to connect base station or chain of base stations to the network. Make sure
the system ID for the relevant base stations are the same otherwise the multi-cell
feature will not work.
Repeaters
Administration and configuration of repeaters of the system
Alarm
Currently not used.
Statistics
Overview of system and call statistics for a system.
Configuration
This shows detail and complete SMART System network settings for base station(s),
HTTP/DNS/DHCP/TFTP server, SIP server, etc.
Syslog
Overall network related events or logs are displayed here (only live feed is shown).
SIP Log
SIP related logs can be retrieved from url link. It is also possible to clear logs from
this feature.

18 T100361E_RD_COBS SMART System Guide
5.2 Home/Status
We describe the parameters found in the Welcome front end home/status of the SMART System
Administration Interface.
Parameter
Description
System information
This base current multi-cell state
Phone Type
Always IPDECT-V2
System Type
This base customer configuration
RF Band
This base RF band setting.
The parameter is software defined in production and relates to the radio
approvals shown on the label of the base.
Current local time
This base local time
Operation time
Operation is operation time for the base since last reboot
RFPI-Address
This base RFPI address
PARK Address
This base PARK address
MAC-Address
This base MAC address
IP-Address
This base IP address
Firmware version
This base firmware version
Firmware URL
Firmware update server address and firmware path on server
Base Station Status
“Idle” : When no calls on base
“In use” : When active calls on base
SIP identity status
List of extensions present at this base station.
Format: “extension”@“this base IP address”(“server name”) followed by
status to the right. Below is listed possible status:
OK: Handset is ok
SIP Error: SIP registration error
Reboot
Reboot after all connections is stopped on base. Connections are active
calls, directory access, firmware update active
Forced Reboot
Reboot immediately.

19 T100361E_RD_COBS SMART System Guide
5.3 Extensions
In this section, we describe the different parameters available whenever the administrator is creating
extensions for handsets. Note, it is not possible to add extensions if no servers are defined. As well the
section describes the administration of extensions and handsets using the extension list and the extension
list menu.
The system can handle maximum 1000 extensions matching 1000 handsets which can be divided between
servers. When 1000 handsets are registered it is not possible to add more extensions. With active multiline
feature the system can handle maximum 1000 extensions. With 4 active lines maximum 250 handsets can
be active in the system.
Note: Within servers or even with multi servers, extensions must always be unique. This means same
extension number on server 1 cannot be re-used on server 2.
5.3.1 Add extension
Parameter
Default Value(s)
Description
Extension
Empty
Handset phone number or SIP username depending on the
setup.
Possible value(s): 8-bit string length
Example: 1024, etc.
Note: The Extension must also be configured in SIP server in
order for this feature to function.
Authentication
User Name
Empty
Username: SIP authentication username
Permitted value(s): 8-bit string length
Authentication
Password
Empty
Password: SIP authentication password.
Permitted value(s): 8-bit string length
Display Name
Empty
Human readable name used for the given extension
Permitted value(s): 8-bit string length

20 T100361E_RD_COBS SMART System Guide
Mailbox Name
Empty
Name of centralised system used to store phone voice
messages that can be retrieved by recipient at a later time.
Valid Input(s): 8-bit string Latin characters for the Name
Mailbox
Number
Empty
Dialled mail box number by long key press on key 1.
Valid Input(s): 0 –9, *, #
Note: Mailbox Number parameter is available only when it’s
enabled from SIP server.
Server
Server 1 IP
FQDN or IP address of SIP server.
Drop down menu to select between the defined Servers of
SMART System Service provider.
Call waiting
feature:
Enabled
Used to enable/disable Call Waiting feature. When disabled a
second incoming call will be rejected. If enabled a second call
will be presented as call waiting.
Broadsoft
Feature Event
Package
Disabled
If enabled the given SIP extension subscribes for the Broadsoft
Application Server Feature Event Package, and it becomes ready
for reception of SIP NOTIFY with status on the following
Broadsoft Server Services:
-Do Not Disturb
-Call Forwarding (Always, Busy, No answer)
The received status will be displayed in the handset idle display.
Reference section 5.3.2
Forwarding
Unconditional
Number
Empty
Number to which incoming calls must be re-routed to
irrespective of the current state of the handset.
Forwarding Unconditional must be enabled to function.
Note: Feature must be enabled in the SIP server before it can
function in the network
Disabled
Forwarding No
Answer Number
Empty
Number to which incoming calls must be re-routed to when
there is no response from the SIP end node.
Forwarding No Answer Number must be enabled to function.
Note: Feature must be enabled in the SIP server before it can
function in the network
Specify delay from call to forward in seconds.
Disabled
90
Forwarding On
Busy Number
Empty
Number to which incoming calls must be re-routed to when SIP
node is busy.
Forwarding On Busy Number must be enabled to function.
Note: Feature must be enabled in the SIP server before it can
function in the network
Disabled