Radio transmitter

from Wikipedia, the free encyclopedia
This article or paragraph presents the situation in Germany . Help us to describe the situation in other countries.

A widely used analogue radio transmitter Motorola Pageboy II
Digital message receiver (for receiving text messages)

A radio alarm receiver ( FME ) - also pager , pager or radio pager (colloquially also occasionally radio alarm clock) - is a small portable radio receiver that is usually used as part of a radio service for alerting purposes and for sending messages to people. The term pager comes from the hotel industry and is reminiscent of the call of a page .

State of the art

Among the radio signal receivers there are systems for building use (only inside buildings), for national and any regional use (inside and outside of buildings). Systems for regional use are available as proprietary systems. The competition is determined by the pricing for the generally available short message services in the GSM or UMTS network with short message service . Systems for building applications are based on the installed radio networks according to the valid standards WLAN according to IEEE 802.11 and DECT . The difference in protocol standards usually prevents the same types of devices from being used in different companies and at different locations.

The difference between the systems for applications inside buildings lies primarily in the required transmission power (regionally up to 2 W EIRP , locally mostly below 100 mW EIRP) and the associated potential for interference as well as in the performance characteristics of the services for the users.

history

The first radio transmitter was developed in 1950 by the American Alfred Gross . They were used by doctors in the New York metropolitan area. This first pager system had a range of approximately 25 miles and doctors paid $ 12 a month for the service. The device was manufactured by the Reevesound Company of New York. It weighed about 200 g.

Older radio signal receivers were implemented in a variety of ways using analog technology. However, according to the current state of the art, these radio signal receivers require an unnecessarily large channel bandwidth . Some of these systems can no longer be used due to changes in the approval conditions.

Newer systems are digitized in modulation and data transmission . However, they do not offer convergence with professional radio equipment or with cellular networks or with wireless in-house telephones. The cause lies in the history of business development with cellular networks and the short message service Short Message Service. The dynamic development of communication costs does not encourage new systems for any regional application. Furthermore, so far no solutions have been offered which are coordinated with the services of IP telephony in WLANs.

outlook

Current procurements will be based on nationwide radio paging networks, the new digital corporate radio equipment and local radio networks, and will also offer end devices with a lower range of functions and thus be cheaper and smaller than a handheld radio, but hardly cheaper than a mobile phone produced in large numbers.

It is questionable whether the special systems can be replaced by devices from other cellular networks (GSM, 3GPP ). The operating strategies of the mobile network operators to date do not ensure that large locations are not overloaded and are therefore not a substitute. In addition, the world's leading GSM Association shows in its study The Role of Mobiles in Disasters and Emergencies that GSM-based mobile phones - with the exception of cell broadcast - are not suitable for alerting and warning the population in the event of natural disasters and other major incidents. With cell broadcast, the necessary configuration effort on the user side is criticized. In addition, the process has not caught on and is rarely used by providers and users.

Provider

In Germany at the beginning of the 1990s, other service providers and products were added to Cityruf , some of which used their own infrastructures or radio systems (e.g. Skyper , Scall , TeLMI , Quix ). With the increasing spread of mobile phones with SMS functionality and the strong concentration on CPP customers (calling party pays), most providers have been displaced.

eMessage is the only provider still on the market in Germany and France. The provider eMessage offers the following technically similar services nationwide: eBos alerting, eSkyper, eBroker, eCityruf, expresso, tatoo and corresponding access platforms. Furthermore, updated weather data are transmitted via this service.

In Austria - beginning in the 1980s - general pager services were offered by Telekom, AirPage and Paging-One. Telekom stopped its service at the end of 2000 for the general public and in 2002 for emergency organizations.

use

BOS

Radio receivers with a signal function are widely used by authorities and organizations with security tasks, for example as an alarm system for the fire brigade to inform their members about an operation. In the meantime, volunteer fire brigades and rescue services in particular are increasingly opting for text alarms with specific operational information in order to save valuable time.

Following a recommendation by the special committees set up in the wake of the Winnenden rampage , the Baden-Württemberg State Ministry of Culture will equip its public schools with pagers from Easter 2012: the police can send warning messages to schools in acute situations. The costs for the necessary data connections are borne by the municipalities, those of the approx. 4,800 devices amounting to more than € 500,000 are borne by the state.

Pagers with message transmission (text, numeric) are used, among other things, in truck inflow control in large manufacturing companies, trading and shipping companies, in municipal winter services (group call), for notifying service and on-call personnel and for monitoring machines and systems with automatically generated Fault messages used. Since the devices are radiation-passive, they are also preferred in safety-relevant areas (nuclear power plants, hospitals, server rooms, etc.).

Different radio services , each with their own frequencies, exist for pagers from different manufacturers . In Germany , for example, there are still city-wide city calls and eBOS alarms, locally there are various BOS alarms (alarm message receivers) and other services.

Amateur radio

Radio amateurs have set up their own radio paging networks . Commercial radio signal receivers, some of which are old stocks of switched-off radio paging networks, are modified for the reception of amateur radio frequencies . In Germany, broadcasts take place mainly on the frequency 439.9875 MHz.

Use in Austria

In the east of Austria , the digital pager network of Notruf Niederösterreich has been used since 2005 to alert the emergency services. Telekom's paging network was discontinued at the end of 2002 as the GSM networks became nationwide. However, this put the aid organizations in distress, as they often triggered an alarm via this Telekom paging network. In remote areas where the pagers worked, cell phones do not yet work with the required reliability because of the so-called dead spots in cellular networks. In 2012, the Lower Austrian fire brigades switched to the digital pager network of Emergency Call Lower Austria.

Belgium

In Belgium, the public limited company ASTRID (All-round semi-cellular trunking radio communication system with integrated dispachtings) operates a nationwide POCSAG-based alerting network, which is currently used by fire and rescue service organizations.

ASTRID only provides the network. Alerting devices and end devices have to be procured by the users themselves.

In order to trigger radio calls, three transmission paths are offered between users and the network: SDSL lines, which are made available by ASTRID; SDS messages which are sent to the paging server via the TETRA network also operated by ASTRID; as well as the transmission via public telephone connections, using the multi-frequency dialing method .

Terminal devices for use in the ASTRID alarm network must be approved by them. A list of the corresponding devices is available on their website.

Luxembourg

In Luxembourg, the Grand Ducal Fire Brigade and Rescue Corps operates its own POCSAG-based pager network in addition to the TETRA network available to it, with which its actors (both honorary and full-time) are alerted. The Oelmann LX8 Viper is used as a pager.

Other use

Pagers are also used in restaurants. If a guest has to wait for a free table or until their meal is ready, they are given a pager. The operator signals the end of his waiting time via acoustic, optical or vibration alarms.

functionality

An FME receives continuously on a certain frequency , which is determined with a crystal or a PLL , and is activated when a precisely defined code is received. This code is transmitted as a 5-tone sequence in analog systems . This 5-tone sequence is based on a ZVEI standard. If the programmed 5-tone sequence is received, the receiver signals this by means of an optical and acoustic alarm; depending on the design, a vibration alarm is also activated. This may be followed by the output of a received message via the loudspeaker. With digital pagers an address code word is transmitted first. If this address is programmed on the pager, the receiver remains switched on for the following message code words. From this a message is composed and displayed, and the pager alerts with visual, acoustic and vibration alarms. The transmission protocol used is usually POCSAG .

While the senders in public networks send both the identifier and the message to a specific recipient, in some networks only the identifiers are sent to a specific recipient. Theoretically, everyone can then receive the message. In the second case, the identifier only switches on the receiving part of the FME, so that practically only the specific recipient or group of recipients receives this message. With activated FME you can hear every message in the reception area of ​​the transmitter. The second type is used, for example, by fire departments in Lower Austria and other federal states for alerting.

Types of pagers

This article or the following section is not adequately provided with supporting documents ( e.g. individual evidence ). Information without sufficient evidence could be removed soon. Please help Wikipedia by researching the information and including good evidence.

There are digital and analog receivers, depending on the type of transmitter .

Analogue radio alarm receivers (FME)

The analog FME are currently still widespread among the authorities and organizations with security tasks in Germany, in Austria the majority has already been converted to digital alarms.

In most cases, the alarm channel is the same as the voice channel of the responsible control center (mostly in the 4-meter band ). Thus, only the corresponding 5-tone sequence has to be modulated on the carrier and the corresponding beeper is alarmed.

The following disadvantages result from this principle, which is easy to implement:

  • In radio networks in which a large number of vehicles are to be dispatched, the channel can quickly become overloaded, since such an alarm occupies the voice channel for around 20 to 30 seconds. This means that the channel is not available to other vehicles during this time, which can, for example, delay important messages such as an emergency doctor's request and is also relatively slow when alarming many resources with individual call addresses.
  • Also, very few analogue detectors have a field strength alarm for technical reasons , so its owner can unexpectedly get into a dead zone and therefore miss an alarm. Such a function must also be carried out by the corresponding radio network through periodic transmissions, which is not the case in Germany. The radio availability can only be checked in such networks through recurring (e.g. daily) trial calls, B. is common in Austria. In doing so, the user can ensure that the pager is triggered in those places where he usually stays (e.g. ambulance guards) or that the detector is positioned in the building in places with safe reception (e.g. firefighter at home).
  • Another problem with analog radio technology is the fact that information here in plain text can easily be intercepted by unauthorized persons with a simple radio scanner . Encryption is not customary for analogue detectors and would be very costly. It is only common in digital radio technology.

Digital alarm receivers (DME)

The digital FME (also: DME for digital signal receiver, POCSAG alarming) are usually operated on a different channel (mainly in the 2-meter band ), so that a major disadvantage of the analog FME, the occupancy of the voice channel, is eliminated. The time required to raise the alarm is also much shorter: After the radio identification code (RIC) of the beeper has been addressed, either a short message (similar to an SMS) or just a few coding bits are transmitted, depending on the operating mode. The coding bits then trigger a voice file stored on the detector (e.g. test alarm or fire alarm ). A combination of both types is also conceivable. Stored, high-quality voice files enable clear and undistorted transmission of operational commands.

Whether a stored voice or text message or a free text sent by the control center is output depends on the construction stage of the DME. Devices of construction stage 1 (DME I) only have stored keywords, DME-II devices can receive and display free texts. The maximum expansion level is offered by a DME III device that converts the received text into speech with the help of a dictionary stored in the device and then reproduces it acoustically. The latest development is a duo device that reads out the text and also shows it on the display.

A home network identifier is also activated in many radio networks (only in Swissphone networks). This enables the user to determine when he is outside his alarm network; the field strength display does not have to be activated. It is only looking for a signal that the digital alarm converter (DAU) usually sends out every three minutes (token ring signal). Some DME have a callback function or a confirmation via a Bluetooth connection to a mobile phone to be sent back to the network so that the dispatcher at the control center can directly assess the efficiency of the alarm when the alarm is raised. However, this has turned out to be not practical, which is why pagers with an integrated GSM module are available. Thanks to the built-in GPS , position-related alarms and position inquiries are also possible.

In the POCSAG alarm there is also the option of a so-called express alarm. With this type of alert, the message receiver is triggered by a programmed radio identification code (RIC), but the control center does not yet send a text. The alarm text comes after the alarm has been issued in the form of a text RIC. This RIC is programmed on all DME and is only evaluated if the DME was previously triggered by the normal RIC. As a result, several RICs can be triggered more quickly one after the other, because the identical text only needs to be transmitted once for several RICs, which enables the emergency services required to be alerted almost simultaneously. This further development of the POCSAG protocol was developed by Swissphone and is under patent protection.

After the introduction of the nationwide TETRA digital radio network BOSNET , the 4 m frequencies, which are still used today for analog alarms with a 5 tone ring , are gradually being abandoned. A financially justifiable transition period of approx. Ten years will give the procurers some time for orientation. Until then, the basic questions must be clarified such as:

TETRA message receiver (TME) in Germany

When the BOSNET is set up, an alarm via TETRA is an option. The states of Bavaria and Hesse have already committed to alerting the emergency services of the authorities and organizations with security tasks via the digital radio network. Each digital device can be individually addressed via a unique ISSI (Individual Short Subscriber Identity). The discussion about passive end devices that have no transmission capability is no longer topical. The TETRA standard does not provide for such a device either. With active TME (APRT = Active Paging Radio Terminal) you can send an automatic receipt and manual feedback to the control center as to whether you can take part in the operation or not. This means that the dispatcher can immediately see how many emergency services are to be expected, and he can carry out a follow-up alarm if necessary. In Bavaria, however, this option will not be activated in the first phase, so that the emergency services will initially not give any feedback. The problem with alerting, however, is the fact that in many federal states no nationwide in-house supply is currently planned, which means that alerting using TETRA does not seem sensible.

The former Hessian project group digital radio tendered the development and delivery of 50,000 TETRA message receivers. The Airbus group with its radio division, at that time still active under the company name Cassidian or EADS, was able to win the tender. From November 19, 2014, the group of experts from the non-police BOS of the State of Hesse was able to carry out the first tests with 100 TETRA pagers of the P8gr type from Airbus. In 2015, a 1000 test was passed in a row in Hesse with the involvement of the non-police BOS. During the two test runs, experience was gained and errors identified, which were then rectified. At the end of 2015, Airbus was able to win the development after certification by the BDBOS in week 45/2015 and the delivery of 50,000 devices for the state of Hesse. Since 2016, the Hessian municipalities have been able to order the pagers with accessories in a shopping cart. The rollout of the TETRA pagers in Hesse started on October 1, 2016. A comparable device from Motorola has been available since the PMR Expo in November 2016. Since 2017, analog alarms have already been switched over to digital alarms via TETRA in some areas in Hesse that are well supplied.

Paging was specified in March 2009 in the form of a Tetra Interoperability Profile in the TETRA standard under TTR 001-21 Callout and is accordingly also specified by the BDBOS in the BOS-IOP guidelines under BIP 05 ALR.

Manufacturer

Well-known manufacturers of radio alarm receivers are or were:

See also

literature

  • Police technical institute of the German police college: Technical guideline of the authorities and organizations with security tasks (BOS): Devices for digital radio alarms
  • The Role of Mobiles in Disasters and Emergencies. GSM Association, December 2005

Web links

Commons : Pagers  - collection of pictures, videos and audio files

Individual evidence

  1. ↑ Why "paging" - where does this term come from? ( Memento of October 30, 2013 in the Internet Archive ) on Pagernetz.at accessed on January 29, 2013
  2. ^ Necrology
  3. ↑ Pocket Radio Pages Doctors Night Or Day. In: Popular Science, January 1951, pp. 104f.
  4. ↑ GSM Association - The Role of Mobiles in Disasters and Emergencies. ( Memento from June 17, 2012 in the Internet Archive ) (PDF; 287 kB) Original version December 2005 (English)
  5. ↑ emessage.de ( Memento from June 4, 2010 in the Internet Archive )
  6. ↑ Ministry of Education equips public schools with alarm devices. In: baden-wuerttemberg.de, Das Landesportal, Schule  ( page no longer available , search in web archives )  Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice. (April 15, 2012)@1@ 2Template: Toter Link / www.baden-wuerttemberg.de  
  7. ↑ Radio call (with Skyper) in amateur radio ( Memento from September 25, 2011 in the Internet Archive ). DO7VLR website. Retrieved November 3, 2010.
  8. ↑ paging in amateur radio . Website of the University of Stuttgart . Retrieved February 5, 2011.
  9. ↑ Milestones - From the idea to the realization ( Memento from October 29, 2013 in the Internet Archive ) on Pagernetz.at accessed on January 29, 2013
  10. ↑ a b Paging - With ASTRID paging, the fire brigade and other emergency services can both easily and quickly call their staff in case of an incident. Retrieved August 5, 2020 .
  11. ↑ Validated Pager 0719. Retrieved August 5, 2020 .
  12. ↑ Technical guideline of the authorities and organizations with security tasks (BOS) - devices for wireless alarms - as of March 2000. Accessed on August 1, 2020 .
  13. ↑ a b Technical guideline of the authorities and organizations with security duties (BOS) - devices for digital wireless alarms - as of April 2011. Accessed on August 1, 2020 .
  14. ^ Patent specification - DE 103 09 612 B4. Retrieved August 1, 2020 .
  15. ↑ BDBOS - alerting