IDM IAD-EX4O Voice Gateway Switching Equipment
24 analog ports with concurrent recording: one unit covers 20-user site access
The IDM IAD-EX4O voice gateway switching equipment supports a maximum of 20 users and up to 24 built-in analog ports, supports the SIP/MGCP protocols, has built-in recording, a range of voice features and security protection, and is suitable for enterprise voice communication access.
The IDM IAD-EX4O 24-channel analog voice access gateway is a voice access switching device for private network sites and the branch offices of small and micro enterprises. Developed by Beijing Ruiguang Jiyuan Digital Technology Co., Ltd., it serves as a professional IP access gateway and analog voice gateway, connecting ordinary telephones, fax machines and analog outside lines to the IP voice network to deliver an efficient private network voice access solution. A single IDM IAD-EX4O provides 24 analog ports, a 20-user capacity and 24 concurrent calls with recording, and is positioned at the voice access layer: downwards it connects analog telephones, fax machines and SIP telephones, and upwards it registers to an IP PBX, a softswitch platform or a carrier IMS network through the SIP, MGCP or IMS protocols. One device covers the enterprise voice communication access of a site with 20 users, without stacking multiple small-capacity gateways. As an optical multiplexer manufacturer with many years of experience in the field, Ruiguang Jiyuan (Raytrans) applies this device widely in government private network optical fiber communication solutions and smart mining communication solutions, providing stable and reliable voice access support for various private network scenarios.
Key Specifications at a Glance: 24 analog ports · 20-user capacity · 24 concurrent calls with recording · 16 GB built-in storage · dual-core 860 MHz processor · 12 VDC/1.5 A DC power supply
What Is an Analog Voice Gateway?
What is an analog voice gateway? In one sentence: it is a device that converts the voice signal of an analog telephone into IP voice data packets, enabling traditional telephones and fax machines to connect to an IP network. In the product showcase, the IDM IAD-EX4O 24-channel analog voice access gateway completes signal conversion and telephone switching in the same machine; it comes with 24 analog ports and also provides 4 IP extension licenses and 20 IP outside line licenses, so analog telephones, IP telephones and agent clients can share the same numbering scheme, and calls inside and outside the site are handled centrally by this device. As a typical analog voice gateway, it can also serve as an IP access gateway, providing basic access capability for private network voice access solutions.
Figure 1: IDM IAD-EX4O voice gateway front panel close-up of indicator LEDs and the layout of the 24 analog ports
The IDM IAD-EX4O offers two installation methods, desktop and rack-mounted; its net weight is 0.72 kg, it is powered by a 12 VDC/1.5 A DC power supply, and its power consumption is 9 W, so it can be placed on a duty desk or installed directly in a site cabinet. The operating environment of the IDM IAD-EX4O is a temperature of 0~40 °C and a relative humidity of 10%90% (non-condensing), and the storage environment is a temperature of -4070 °C and a relative humidity of 5%~90% (non-condensing), so conventional indoor equipment room and duty room conditions are sufficient. The IDM IAD-EX4O provides 3.5 kV lightning protection and, together with busy tone detection and reverse polarity detection on the analog outside lines, can adapt to private network equipment rooms and outside line lead-in scenarios. As an optical multiplexer manufacturer, Ruiguang Jiyuan (Raytrans) has long provided voice access equipment for government private network optical fiber communication solutions and smart mining communication solutions, and this model is one member of its enterprise voice communication access product line.
Which Call Control Protocols and Network Access Modes Are Supported?
Which call control protocols a voice gateway supports determines whether it can interconnect with an existing platform. The IDM IAD-EX4O supports three types of call control protocols at the same time: SIP/UDP and SIP/TCP (RFC3261), the IMS platform (3GPP) and MGCP (RFC3435). SIP-based IP PBX and softswitch platforms use the SIP channel; service provisioning on a carrier or private network IMS network goes through the IMS platform channel; some in-service devices still use MGCP, and the IDM IAD-EX4O can also register and interconnect with them, facilitating the phased upgrade of an existing voice network.
On the network side, the IDM IAD-EX4O supports Telnet, SSH, HTTP, HTTPS, DHCP client, PPPoE client, DNS (ASRN records), STUN, OpenVPN client and 802.1X. The SIP trunk supports IMS, multi-platform registration and calling and Skype Connect, and the analog outside lines support caller ID, busy tone detection and reverse polarity detection. The traversal service of the IDM IAD-EX4O enables the registration of external network extensions, branch networking and mobile office work; IP telephones support plug-and-play, and SIP telephones and various IP terminals can all be connected smoothly.
Overview of Functions and Performance Parameters
Voice Services and Switching Functions
Function | Description |
|---|---|
Call control | SIP/UDP and SIP/TCP (RFC3261), the IMS platform (3GPP), MGCP (RFC3435) |
Caller ID | Belcore Type 1&2, ETSI, BT, NTT, DTMF and other standards |
Voice codec | G.711 (a/u), G.729B, G.722.2, G.722 |
DTMF sending | In-band voice communication, RFC2833, SIP-INFO |
Fax | G.711 transparent transmission, T.38 fax, compatible with G3 fax machines, rate 33.6 kbps (transparent transmission/T.38 V3) |
Line release mode | Busy tone detection, reverse polarity detection, line release on power failure |
Voice quality enhancement technologies | Echo cancellation (G.168-2004, tail length 64 ms), automatic jitter buffer adjustment |
Intelligent switchboard/attendant console | Working day/non-working day time periods, incoming call queuing, operator grouping, multilingual/multi-level voice menus, switchboard templates, switchboard frames, rapid handling of calls from VIP customers (without dialing an extension number) |
Dialing | Abbreviated dialing, outgoing line selection, least-cost routing, automatic route selection, automatic prefixing of "0" for non-local mobile numbers |
Call features | Call hold, call transfer, call waiting, three-party call, simultaneous ringing, distinctive ringing, do not disturb (DND), barge-in/barge-in disabled, monitoring/monitoring disabled, secretary, hotline (immediate/delayed), call pickup/call pickup disabled, call forwarding, call diversion, one number with two devices, call barring, group hunting, number conversion, external-to-external transfer, etc. |
DISA | Calling number authentication, authentication by dialing a feature code |
Recording | Built-in recording; recordings are managed through the recording, query and recording management systems |
Message waiting notification | Reverse polarity/FSK/high-voltage (neon) |
Analog outside line | Caller ID, busy tone detection, reverse polarity detection |
SIP trunk | IMS, multi-platform registration and calling, Skype Connect |
Telephone status display | Extension status subscription (BLF) |
Security and O&M Management Functions
Function | Description |
|---|---|
Port customization | SIP port, HTTP/HTTPS access port, RTP port |
Encryption | SIP signaling encryption, media stream encryption, encrypted import/export of configuration files, password/PIN code encryption |
IP extension protection | Blocking external-network IP extensions from dialing outside lines, User-Agent verification, protection against brute-force cracking of IP extension passwords |
Anti-intrusion | Malicious IP locking, access whitelist, dynamic defense, static defense |
Security level | Three levels available: high, medium and low |
Application interface | API (XML/HTTP) |
Logs | 8-level log management, Syslog, 16 GB built-in storage |
Data capture | Port voice capture, packet capture |
Configuration | Configuration import/export, restore/backup |
Status and alarms | Operating status, alarm information |
Network management | Supports the network management system and third-party network management systems (TR-069, SNMP) |
Lightning protection | Provides 3.5 kV lightning protection |
Hardware and Performance Specifications
Item | Parameter/Specification | Description/Applicable Conditions |
|---|---|---|
User capacity | 20 users | A single unit covers the scale of one site |
Built-in analog ports | 24 | Directly connects analog telephones and fax machines |
IP extension licenses | 4 | Connects IP telephones or softphones |
IP outside line licenses | 20 | SIP trunk registration |
Number of simultaneous calls (with recording) | 24 | Calls and recording in parallel |
Agent client concurrency | 20 | Access for computer agent seats |
Processor | Dual-core, 860 MHz | Call processing and control of the unit |
System memory | 256 MB | — |
Flash memory | 16 MB | — |
Built-in storage | 16 GB | Storage for recordings, captures and logs |
Weight (net weight) | 0.72 kg | — |
DC power supply specification | 12 VDC/1.5 A | DC power supply |
Installation method | Desktop/rack-mounted | Duty desk or site cabinet |
Power consumption | 9 W | — |
Operating environment | Temperature 0~40 °C; relative humidity 10%~90% (non-condensing) | Indoor equipment room and duty room |
Storage environment | Temperature -40~70 °C; relative humidity 5%~90% (non-condensing) | Warehousing and transportation |
What Can a Voice Gateway with Built-in Recording Record, and How Is Fault Tracing Carried Out?
The value of a voice gateway with built-in recording lies in keeping call evidence locally at the site. The IDM IAD-EX4O provides built-in recording, and recordings are managed through the recording, query and recording management systems; the number of simultaneous calls (with recording) is 24, which means that the 24 analog ports can record while a call is in progress. The IDM IAD-EX4O has 16 GB of built-in storage, both port voice capture and packet capture are written into the onboard storage, and on the log side it provides 8-level log management and Syslog reporting.
During fault tracing the two types of capture data have different roles: port voice capture is used to review call content, while packet capture is used to analyze the interaction between signaling and media streams. Both types of data are obtained inside the device, so a site can complete on-site evidence collection without additionally configuring an external recording server or a packet capture device. Message waiting notification supports three modes: reverse polarity, FSK and high-voltage (neon). As for the export and backup methods for recordings and captured data, the manufacturer's technical documentation and commercial confirmation shall prevail. Around government private network optical fiber communication solutions, smart mining communication solutions and private network voice access solutions, Ruiguang Jiyuan (Raytrans) can provide a complete set of enterprise voice communication access ranging from optical multiplexers to devices such as analog voice gateways, IP access gateways and SIP telephones.
Private Network Boundary Security: Dual Encryption of Signaling and Media
The voice boundary risk of a private network site mainly comes from two directions: signaling being intercepted or forged, and media streams being bypassed and monitored. The IDM IAD-EX4O adopts the dual means of SIP signaling encryption and media stream encryption, and also encrypts the import/export of configuration files as well as passwords/PIN codes; against illegal registration attempts, the IP extension side provides three constraints: blocking external-network IP extensions from dialing outside lines, User-Agent verification and protection against brute-force cracking of IP extension passwords.
For intrusion behavior, the IDM IAD-EX4O provides malicious IP locking, an access whitelist, dynamic defense and static defense, and the protection strength can be switched as a whole among three security levels: high, medium and low. The port customization capability allows the SIP port, the HTTP/HTTPS access port and the RTP port to be changed to non-default values, reducing the probability of being hit by scans; the security configuration itself can be imported/exported encrypted together with the configuration file, making it easy to deploy a batch of devices on a unified baseline.
Typical Application Scenarios
Electric Power and Energy Private Network Sites: Duty Telephone Access and Call Tracing
Substations, switching stations and energy sites in the electric power and energy industry usually keep a large number of analog telephones, and calls between the duty room and dispatching need to be traceable. The IDM IAD-EX4O 24-channel analog voice access gateway comes with 24 analog ports and can directly connect the analog telephones and fax machines in the site, then register with the upper-level softswitch platform over SIP or IMS; the 20-user capacity matches the scale of a single site. The 24 concurrent calls with recording allow both daily dispatching calls and incident-handling calls to be retained, and the 16 GB built-in storage keeps the recordings on the site side, so even if the upper-level network is interrupted, the local call records at the site are not lost.
Rail Transit and Utility Tunnel Communication: Voice Aggregation of Trackside Telephones
The communication sites of rail transit and underground utility tunnels are scattered and the passages are enclosed, so analog telephones are a reliable means at the far end. The IDM IAD-EX4O supports two installation methods, desktop and rack-mounted, and can be placed in a section equipment cabinet or a utility tunnel communication box to aggregate the analog telephones along the line into the IP voice network; the 12 VDC/1.5 A DC power supply and 9 W power consumption make it easy to draw power and operate inside a communication box, and the 0~40 °C operating temperature suits indoor equipment room and equipment box environments. SIP signaling encryption and media stream encryption ensure that call content is not bypassed, while malicious IP locking and the access whitelist restrict access by unauthorized terminals.
Unattended Equipment Rooms and Pump Stations: Built-in Capture Replaces External Recording Equipment
Voice failures at unattended equipment rooms and pump stations are often discovered only afterwards, and it is inconvenient to install additional equipment on site. The IDM IAD-EX4O builds 16 GB of storage, port voice capture and packet capture into the unit, so the site no longer needs an external recording server; O&M personnel can check the call setup process through the logs and captured data and determine whether the problem lies in the line, the telephone or the platform side, reducing site visits. For a pump station with only a small number of extensions, 4 IP extension licenses are enough to cover IP telephones and softphones, while caller ID, busy tone detection and reverse polarity detection on the analog outside lines provide compatibility with existing outside line access.
How to Select a 24-Channel Analog Voice Access Gateway?
When selecting a 24-channel analog voice gateway, it is advisable to check item by item in the order of "ports first, then protocols, then security", and to compare peripheral functions only after the hard metrics are met.
Selection Dimension | Recommended Checks | Basis for Judgment |
|---|---|---|
Analog port count | Total number of analog telephones and fax machines at the site | The IDM IAD-EX4O comes with 24 analog ports |
Concurrency and recording | Whether calls and recording must be carried out at the same time | Number of simultaneous calls (with recording): 24 |
Protocol interconnection | Whether the upper-level platform uses SIP, IMS or MGCP | The IDM IAD-EX4O supports all three types of call control protocols |
Users and agents | Number of telephones and number of agent clients | User capacity 20, agent client concurrency 20 |
Security requirements | Whether signaling and media encryption and an access whitelist are needed | SIP signaling encryption, media stream encryption, malicious IP locking, access whitelist |
Fault tracing | Whether local recording and packet capture are needed | Built-in recording, port voice capture, packet capture, 16 GB storage |
Installation and power supply | Desktop or cabinet, DC power supply conditions | Desktop/rack-mounted installation, 12 VDC/1.5 A power supply |
It should be noted that 24 analog ports and a 20-user capacity correspond to a single-site scale. If the number of analog telephones exceeds 24, or unified dispatching across sites is required, the IDM IAD-EX4O should be used as an access-layer device together with the upper-level platform, deployed by horizontally stacking units according to the number of sites. An operating temperature of 0~40 °C corresponds to equipment room and duty room conditions, and outdoor cabinet scenarios require separate confirmation of the installation conditions.
Differentiated Value
Differentiated Selling Point | Corresponding Capability | Value to Users |
|---|---|---|
24 analog ports + 24 concurrent recordings | 24 built-in analog ports, number of simultaneous calls (with recording) 24 | A single unit supports the voice access of a 20-user private network site, and the analog telephones do not need to be replaced |
Built-in 16 GB storage and capture | Port voice capture, packet capture, 8-level logs and Syslog | Fault tracing is completed inside the device, and the site needs no external recording or packet capture equipment |
Dual encryption of SIP signaling and media streams | SIP signaling encryption, media stream encryption, malicious IP locking, access whitelist | The private network voice boundary is more controllable, making illegal registration and bypass monitoring difficult |
Conclusion
The IDM IAD-EX4O 24-channel analog voice access gateway does three things in one compact device: first, density — 24 analog ports and a 20-user capacity correspond to single-site voice access, and 24 concurrent calls with recording keep calls and records in step; second, tracing — the 16 GB built-in storage together with port voice capture, packet capture and 8-level logs means that fault location does not require external equipment; third, boundary security — SIP signaling encryption and media stream encryption combined with malicious IP locking and an access whitelist guard the entrance to private network voice access. During selection, first check the number of analog ports and the concurrent recording requirement, then confirm the upper-level platform protocol and security policy, and finally decide the number of units to deploy according to the site scale.
Function | Description |
|---|---|
Port customization | SIP port, HTTP/HTTPS access port, RTP port |
Encryption | SIP signaling encryption, media stream encryption, encrypted import/export of configuration files, password/PIN code encryption |
IP extension protection | Blocking external-network IP extensions from dialing outside lines, User-Agent verification, protection against brute-force cracking of IP extension passwords |
Anti-intrusion | Malicious IP locking, access whitelist, dynamic defense, static defense |
Security level | Three levels available: high, medium and low |
Application interface | API (XML/HTTP) |
Logs | 8-level log management, Syslog, 16 GB built-in storage |
Data capture | Port voice capture, packet capture |
Configuration | Configuration import/export, restore/backup |
Status and alarms | Operating status, alarm information |
Network management | Supports the network management system and third-party network management systems (TR-069, SNMP) |
Lightning protection | Provides 3.5 kV lightning protection |
Hardware and Performance Specifications
Item | Parameter/Specification | Description/Applicable Conditions |
|---|---|---|
User capacity | 20 users | A single unit covers the scale of one site |
Built-in analog ports | 24 | Directly connects analog telephones and fax machines |
IP extension licenses | 4 | Connects IP telephones or softphones |
IP outside line licenses | 20 | SIP trunk registration |
Number of simultaneous calls (with recording) | 24 | Calls and recording in parallel |
Agent client concurrency | 20 | Access for computer agent seats |
Processor | Dual-core, 860 MHz | Call processing and control of the unit |
System memory | 256 MB | — |
Flash memory | 16 MB | — |
Built-in storage | 16 GB | Storage for recordings, captures and logs |
Weight (net weight) | 0.72 kg | — |
DC power supply specification | 12 VDC/1.5 A | DC power supply |
Installation method | Desktop/rack-mounted | Duty desk or site cabinet |
Power consumption | 9 W | — |
Operating environment | Temperature 0~40 °C; relative humidity 10%~90% (non-condensing) | Indoor equipment room and duty room |
Storage environment | Temperature -40~70 °C; relative humidity 5%~90% (non-condensing) | Warehousing and transportation |
What Can a Voice Gateway with Built-in Recording Record, and How Is Fault Tracing Carried Out?
The value of a voice gateway with built-in recording lies in keeping call evidence locally at the site. The IDM IAD-EX4O provides built-in recording, and recordings are managed through the recording, query and recording management systems; the number of simultaneous calls (with recording) is 24, which means that the 24 analog ports can record while a call is in progress. The IDM IAD-EX4O has 16 GB of built-in storage, into which both port voice capture and packet capture are written, and on the log side it provides 8-level log management and Syslog reporting.
During fault tracing the two types of capture data have different roles: port voice capture is used to review call content, while packet capture is used to analyze the interaction between signaling and media streams. Both types of data are obtained inside the device, so a site can complete on-site evidence collection without additionally configuring an external recording server or a packet capture device. Message waiting notification supports three modes: reverse polarity, FSK and high-voltage (neon). As for the export and backup methods for recordings and captured data, the manufacturer's technical documentation and commercial confirmation shall prevail. Around government private network optical fiber communication solutions, smart mining communication solutions and private network voice access solutions, Ruiguang Jiyuan (Raytrans) can provide a complete set of enterprise voice communication access ranging from optical multiplexers to devices such as analog voice gateways, IP access gateways and SIP telephones.
Private Network Boundary Security: Dual Encryption of Signaling and Media
The voice boundary risk of a private network site mainly comes from two directions: signaling being intercepted or forged, and media streams being bypassed and monitored. The IDM IAD-EX4O adopts the dual means of SIP signaling encryption and media stream encryption, and also encrypts the import/export of configuration files as well as passwords/PIN codes; against illegal registration attempts, the IP extension side provides three constraints: blocking external-network IP extensions from dialing outside lines, User-Agent verification and protection against brute-force cracking of IP extension passwords.
For intrusion behavior, the IDM IAD-EX4O provides malicious IP locking, an access whitelist, dynamic defense and static defense, and the protection strength can be switched as a whole among three security levels: high, medium and low. The port customization capability allows the SIP port, the HTTP/HTTPS access port and the RTP port to be changed to non-default values, reducing the probability of being hit by scans; the security configuration itself can be imported/exported encrypted together with the configuration file, making it easy to deploy a batch of devices on a unified baseline.
Typical Application Scenarios
Electric Power and Energy Private Network Sites: Duty Telephone Access and Call Tracing
Substations, switching stations and energy sites in the electric power and energy industry usually keep a large number of analog telephones, and calls between the duty room and dispatching need to be traceable. The IDM IAD-EX4O 24-channel analog voice access gateway comes with 24 analog ports and can directly connect the analog telephones and fax machines in the site, then register with the upper-level softswitch platform over SIP or IMS; the 20-user capacity matches the scale of a single site. The 24 concurrent calls with recording allow both daily dispatching calls and incident-handling calls to be retained, and the 16 GB built-in storage keeps the recordings on the site side, so even if the upper-level network is interrupted, the local call records at the site are not lost.
Rail Transit and Utility Tunnel Communication: Voice Aggregation of Telephones Along the Line
The communication sites of rail transit and underground utility tunnels are scattered and the passages are enclosed, so analog telephones are a reliable means at the far end. The IDM IAD-EX4O supports two installation methods, desktop and rack-mounted, and can be placed in a section equipment cabinet or a utility tunnel communication box to aggregate the analog telephones along the line into the IP voice network; the 12 VDC/1.5 A DC power supply and 9 W power consumption make it easy to draw power and operate inside a communication box, and the 0~40 °C operating temperature suits indoor equipment room and equipment box environments. SIP signaling encryption and media stream encryption ensure that call content is not bypassed, while malicious IP locking and the access whitelist restrict access by unauthorized terminals.
Unattended Equipment Rooms and Pumping Stations: Built-in Capture Replaces External Recording Equipment
Voice failures at unattended equipment rooms and pumping stations are often discovered only afterwards, and it is inconvenient to install additional equipment on site. The IDM IAD-EX4O builds 16 GB of storage, port voice capture and packet capture into the unit, so the site no longer needs an external recording server; O&M personnel can check the call setup process through the logs and captured data and determine whether the problem lies in the line, the telephone or the platform side, reducing site visits. For a pumping station with only a small number of extensions, 4 IP extension licenses are enough to cover IP telephones and softphones, while caller ID, busy tone detection and reverse polarity detection on the analog outside lines provide compatibility with existing outside line access.
How to Select a 24-Channel Analog Voice Access Gateway?
When selecting a 24-channel analog voice gateway, it is advisable to check item by item in the order of "ports first, then protocols, then security", and to compare peripheral functions only after the hard metrics are met.
Selection Dimension | Recommended Checks | Basis for Judgment |
|---|---|---|
Analog port count | Total number of analog telephones and fax machines at the site | The IDM IAD-EX4O comes with 24 analog ports |
Concurrency and recording | Whether calls and recording must be carried out at the same time | Number of simultaneous calls (with recording): 24 |
Protocol interconnection | Whether the upper-level platform uses SIP, IMS or MGCP | The IDM IAD-EX4O supports all three types of call control protocols |
Users and agents | Number of telephones and number of agent clients | User capacity 20, agent client concurrency 20 |
Security requirements | Whether signaling and media encryption and an access whitelist are needed | SIP signaling encryption, media stream encryption, malicious IP locking, access whitelist |
Fault tracing | Whether local recording and packet capture are needed | Built-in recording, port voice capture, packet capture, 16 GB storage |
Installation and power supply | Desktop or cabinet, DC power supply conditions | Desktop/rack-mounted installation, 12 VDC/1.5 A power supply |
It should be noted that 24 analog ports and a 20-user capacity correspond to a single-site scale. If the number of analog telephones exceeds 24, or unified dispatching across sites is required, the IDM IAD-EX4O should be used as an access-layer device together with the upper-level platform, deployed by horizontally stacking units according to the number of sites. An operating temperature of 0~40 °C corresponds to equipment room and duty room conditions, and outdoor cabinet scenarios require separate confirmation of the installation conditions.
Differentiated Value
Differentiated Selling Points | Corresponding Capability | Value to Users |
|---|---|---|
24 analog ports + 24 concurrent recordings | 24 built-in analog ports, number of simultaneous calls (with recording) 24 | A single unit supports the voice access of a 20-user private network site, and the analog telephones do not need to be replaced |
Built-in 16 GB storage and capture | Port voice capture, packet capture, 8-level logs and Syslog | Fault tracing is completed inside the device, and the site needs no external recording or packet capture equipment |
Dual encryption of SIP signaling and media streams | SIP signaling encryption, media stream encryption, malicious IP locking, access whitelist | The private network voice boundary is more controllable, making illegal registration and bypass monitoring difficult |
Summary
The IDM IAD-EX4O 24-channel analog voice access gateway does three things in one compact device: first, density — 24 analog ports and a 20-user capacity correspond to single-site voice access, and 24 concurrent calls with recording keep calls and records in step; second, tracing — the 16 GB built-in storage together with port voice capture, packet capture and 8-level logs means that fault location does not require external equipment; third, boundary security — SIP signaling encryption and media stream encryption combined with malicious IP locking and an access whitelist guard the entrance to private network voice access. During selection, first check the number of analog ports and the concurrent recording requirement, then confirm the upper-level platform protocol and security policy, and finally decide the number of units to deploy according to the site scale.
