Portable transceiver communications have, since their inception, specific applications, capabilities, and limitations. Their applications and capabilities have increased significantly along with the development of technology. Certain limitations, however, remained the same, although some ways were found to overcome them.

One of the most important limitations has always been range. Especially in urban environments the range of portable transceivers is limited, from a few hundred meters to a few kilometers, due to buildings and other obstacles. One solution is to install repeaters in high places but this requires equipment, installation, maintenance and special permits.

Another limitation, which can be overcomed, but again with special costs and several procedures, is the license to operate a special radio network. To complete a professional radio network there is a requirement to obtain a license. Although this process has been relatively simplified in recent years, thanks to the efforts of the relevant authorities, it remains time-consuming and at some cost.

The skyrocketing use of mobile phones in recent decades has led to the construction of a literally global network of cell towers used to relay the signal and interconnect mobile devices. One may use their mobile phone to communicate with other devices, practically without range restrictions and at low cost.

It is therefore logical, that this already existing global mobile telephony network and more specifically the part of it that has to do with the data stream find a way to be used by portable transceiver devices. These new devices offer two very important advantages, among others, in relation to the classic portable transceivers. Unlimited range (where there is a mobile phone network or even WiFi) and radio network integration without the need for a license since the frequencies used are for use by the general public.

The names given to these devices are various and interesting. While the classic portable transceivers are usually called walkie talkies, the new type of transceivers are called either POC (PTT over cellular) transceivers, or LTE 4G (Long Term Evolution) transceivers.

To complete a network with POC transceivers (for the sake of brevity let's use this name) one needs three things:

1. The devices

2. Connection to interface and communications server

3. A SIM card with data per radio

Regarding τηε devices, we present on this page the best and most suitable for professional use, in our opinion, DN-495 transceiver of the British company Entel.

In order to complete communications, as well as the multitude of functions offered by a network with POC devices, the devices must be interconnected with each other, but also with one or more network managers (dispatchers), if necessary, through specialized servers. FreeBytes recommends and supports the servers of the German company Tassta, for which a different presentation will be made.

The British house Entel has been offering excellent models of high-quality transceivers for many years. The DN-495 model is of particular interest since it is a POC model with quality specifications, resistance to harsh environments and particularly easy to use. Let's see some of its features and specifications.

Environmental protection - IP68 (2 Meters for 4 hours) Entel's radios are approved to IP68 (2 Meters for 4 hours) rated construction, which means that they are dust protected and fully Submersible (even with the accessory cover removed).

MILSTD 810C/D/E/F/G - Meeting MIL-STD 810C/D/E/F/G and providing commercial grade construction for tough, enduring performance. Entel's radios conform to stringent standards, enabling them to withstand the everyday rigours of shock, vibration and the corrosive effects of dust and moisture, ensuring many years of trouble free use.

Outstanding Audio - Entel’s radios offer best-in-class performance with natural-sounding digital audio.

Li-Ion battery technology & improved talk time - Entel's radios are supplied with the latest, high-capacity, intelligent Lithium-Ion battery technology as standard. One key advantage of Lithium-Ion battery technology is the way it eliminates ‘memory effect’, meaning that there is no need to fully discharge your battery before recharging. As a result of this, you are assured of a full charge each and every time you take your Entel battery from its charger.

High contrast white on black OLED display - Entel's radios benefit from a high contrast white on black OLED display that delivers superior readability in varying light conditions adding to the radios intuitive user interface.

Spanish language support Entel's radios support additionally support Spanish language, if your have a requirement for another language please contact your Entel representative.

Emergency button - By pressing the emergency button the radio will instantly send an alarm call to other radio(s) as well as sounding a local alarm. On receiving display models the radios unique ID / Alias is also displayed.

Lone-Worker Alarm - Entel’s Lone-Worker alarm is designed to protect lone workers. The radios Lone-Worker timer checks the radios user is OK; if no response is received, the radio will automatically send an alarm call to other radio(s). The local alarm additionally alerts non-radio users in the vicinity to the emergency. Should someone fall and become unconscious, the optional Man-Down sensor can automatically send an alarm. On receiving display models the radios unique ID / Alias is also displayed.

Man-Down Alarm - Entel’s Man-Down alarm is also designed to protect lone workers. Should someone fall and become unconscious, Man-Down sensor automatically sends an alarm. call to other radio(s). The local alarm additionally alerts non-radio users in the vicinity to the emergency. On receiving display models the radios unique ID / Alias is also displayed.

GPS - Entel's GPS equipped radios can be configured to send their location for both management and safety purposes. This information can be displayed and managed via the PC Dispatchers map.

Bluetooth - Entel's Bluetooth enabled radios support our range of Bluetooth audio accessories.

WiFi - In addition to cellular networks DN400 radios can also connect to WiFi enabling communications where there is no cellular coverage, e.g. underground.

Full Duplex - DN400 emergency calls are transmitted full duplex meaning you can hear and speak at the same time (just like a phone). Full duplex regular calls will be introduced Q1 2021.

AES 256 bit Encryption - Entel includes this highest form of encryption as standard in its DN400 radios

Individual Calling - As is suggests this enables you to have a 1-2-1 call where only you and the person you called is party to the conversation. You have the option to ring the radio and wait for the person to answer or make an instant call without ringing first.

Group Calling - This is the most popular form of two-way radio call, it enables you to instantly address two or more radios at once. One or more groups can be programmed into your radios allowing for multiple user groups.

Multiple receive groups - This enables you to monitor two or more groups, e.g. a manager needs to monitor the Cleaning and Maintenance groups he manages.

Caller ID - This is just like a mobile phone, displaying the radios number or alias, e.g. 'Bob', 'Security Hut', 'Reception', etc.

Presence Check - This tells you how many users are on-line in your group and enables you to see who is on-line in your contact list before you try to call them.

Programmable buttons - To ensure your Entel radio meets your exact need its buttons can be programmed with the exact features you need.

Gold plated accessory connector - The radios multi-pin interface and Micro-USB socket are both submersible and gold-plated to minimise any risk of damage and protect against corrosion.

Locking accessory connector - All Entel accessories incorporate a robust locking connector and the radios accessory socket has been specifically designed so that when an accessory is secured to the portable, the connection can withstand any amount of punishment; from dropping to careless misuse.

Accessory audio tailoring - Entel's radios identify the attached accessory and automatically adjust its settings ensuring the most natural and readable audio possible is delivered even with bone conductive accessories and breathing apparatus com kits.

Over the air (OTA) programmable - Entel's DN400 radios can be re-programmed / updated over the air without ever having to visit site saving considerable time and expense as well as delivering a far superior customer support experience.

Scan - DN radios have an advanced scan function allowing you to instantly monitor several channels (groups) at once without any of the delays associated with traditional two-way radios.

All call - This is the ability to call all radios on your system at once. This is especially useful when making important announcements such as an emergency safety call etc.

Transmit interrupt - This is the ability to stop all conversations on the channel and make a high priority important announcement / call. Entel's DN400 radios support 99 levels of priority call. Emergency calls always have the highest priority ensuring they have the best possibility of being received without delay.

Lost network connection audible warning on PTT - If you don't have a network connection and try to press PTT the DN400 radio will emit a tone warning of no network connection.

No one else in the group audible warning on PTT - If no one else is in the group and try to press PTT the DN400 radio will emit a tone warning there are no other users in the group.

Send message from accessory socket - this option allows you to send free format text messages from your radios accessory socket, for example from a BMS or Fire alarm panel.

Contact list search function - with larger systems finding the contact you want to call can be time consuming, the addition of a contact list search function will significantly aid in locating the contact you are looking for.

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