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Telephone Interconnect on Private Mobile Radio Channels |
This information sheet helps to explain what telephone interconnect is and when its use is acceptable on Private Mobile Radio.
"Telephone interconnect" is used here to describe the facilities allowing mobile radio users access into either a public telephone network (such as those run by BT, Mercury etc.), or access to an organisation's own switchboard and associated internal telephone extensions in an office. These are called respectively, Public Switched Telephone Network (PSTN) and Private Automatic Branch Exchange (PABX) or Private Branch Exchange (PBX) connection. For the purpose of licensing policy PABX and PBX are counted as exactly the same and for simplicity only the term PABX has been used.
It is possible for calls to be made either from the mobile to the telephone network or in the reverse direction. These are referred to as outgoing and incoming calls respectively.
Private Mobile Radio is intended for those users who pass a large number of short business related messages. Typical users are those controlling fleets of taxis, national couriers, breakdown organisations etc.
A busy mobile radio channel may easily pass in excess of 100 messages an hour, each of which can last around 15 seconds. Because of the pressure of demand on PMR channels in many parts of the UK, most users have to share channels, taking it in turn to pass messages when the radio channel is free of traffic.
Mobile telephone calls, on the other hand, not only tend to last much longer than PMR messages but the call set up time has also to be taken into account. On cellular radio systems the average telephone call is significantly longer. If PMR users were allowed unrestricted use of telephone interconnect, the PMR channels that are available would become even more congested and other users would often be prevented from using the channel.
Telephone interconnect facilities may not be used on PMR systems unless certain conditions are met and such a facility has been detailed on the appropriate licence schedule.
Telephone interconnect requires:
The radio transmitting apparatus must, for type approval purposes, be approved under Section 84 of the Telecom Act.
Systems licensed under the Telecom Act (Section 13.3.7), other than public network operator licences, generally require all apparatus comprised in, and connected to such systems to be approved under Section 22 of the Telecom Act.
The British Approvals Board for Telecommunications (BABT) deals with approvals under Section 22 of the Telecom Act. Equipment approved by BABT may carry the "green circle" approved mark. Equipment cannot be used for telephone interconnect with the PSTN unless a BABT certificate authorises direct connection to the PSTN.
Any applicant granted interconnect must use equipment approved by BABT only for the purposes stated in the certificate. Details of the interconnect unit, together with approval numbers issued by BABT should accompany the application to the Radiocommunications Agency for authority to operate telephone interconnect.
Details for most of the approved interconnect units are held within the Agency's Private Business Systems Section. BABT have requested this information be submitted with every application. The list of approved units changes as BABT approval is granted to new equipment. Production of the BABT certificate should be possible if requested from the supplier or manufacturer of the unit. As previously detailed this certificate outlines the facilities for which the unit is permitted.
Various categories for interconnect use are considered by the Agency:
For this category of licensee there is normally no WT Act licence restriction on either PSTN or PABX interconnect. No allowance will be made however if an interconnect facility results in a licensee failing to comply with minimum mobile loading requirements. Authority to use interconnect must be detailed on the licence schedule before use is permitted.
For exceptional reasons, the Agency may grant sole use of a channel to a licensee, either regionally or nationally. In these cases applications will be considered for both PSTN and PABX interconnect. If granted there will be no restrictions placed upon incoming or outgoing calls, or time of day for use. The parameters set out below which affect call duration will apply. Sole use of a channel cannot, however, be guaranteed indefinitely and if an exclusive channel becomes shared the restrictions for shared channels may be applied.
Similar consideration to wide area exclusive use (above) will be given to both PSTN and PABX interconnect. On-site is normally contained on a local site e.g. a shopping precinct. The antenna and ERP engineering normally confine the transmissions to within a radius of 3 Km or less. The definition for on-site requires an antenna height of less than 10 metres above ground level with an ERP of 2 watts or less. The limitations contained below will apply to this type of service. It is strongly recommended that Short Form Dialling facilities are used. There is no requirement to limit the number of PABX extensions connected.
This category of authorisation applies to licensees who operate on
shared channels and covers the majority of PMR users. Agreement for PSTN interconnect can
be given for dial-in connection only normally between the hours of midnight and 8.00 am.
This is for incoming calls only. OFTEL recommends that prior to the connection the caller
should be informed that they will be speaking over a radio link; that they may be
overheard, and that the quality of communication may be less than that of a telephone.
Callers should be told that it is not possible for both parties to speak at the same time.
The system parameters set out below will apply. Except in exceptional circumstances, no
extension to the above hours will be permitted. Consideration will be given to outgoing
calls only for connection to 999 emergency services.
This must be by Short Form Dialling.
PABX connection on shared channels will not have the restriction against day and time use, but will be subject to the system limitations given below. The number of contractible extensions is limited to a maximum of 10. Consideration will be given to requests for PSTN interconnect for emergency 999 calls only. This must be by Short Form Dialling. It should be understood that it is not possible to operate interconnect without a fixed base station.
Telephone interconnect systems presently use two forms of dialling. Dual Tone Multi Frequency (DTMF) and Short Form Dialling. The DTMF keypad allows a mobile full access to any number on a PABX and, if the connection is there, to the PSTN as well. To prevent channels from becoming too congested the interconnect unit must limit the availability of telephone extensions to the levels contained above.
It should be remembered that the more mobiles provided with access to telephone numbers, and telephone extensions to mobiles, the more the system will be congested. No additional assignments will be made to a licensee when there is channel congestion as a result of the use of an interconnect facility.
All interconnection systems must not use full duplex operation unless the applicant is the sole user of the channel either regionally or nationally. In those circumstances duplex operation will be considered, although it is less likely that it will be granted on a regional basis. Semi duplex or simplex operation may be utilised.
The following system parameters for any connection to the PABX/PSTN are required:
Numbers, such as those beginning with 0898 etc., or providing a "dial in and listen" service must be barred.
Existing licensees requiring the addition of an interconnect facility to their licence, should write to their normal contact point within the Radiocommunications Agency, quoting the reference number of the licence. There can be no guarantee that interconnection will be permitted. Applicants should not enter into any commitments to buy equipment until the Agency has approved interconnect by adding a suitable clause to the licence schedule.
Full equipment details of the interconnect unit should be provided with the application together with the BABT approval number. Any application not containing this is liable to be delayed.
It is a standard condition of all licences issued under the WT Acts, that no interference should be caused to other radio users. After authorising telephone interconnection in a particular case, if it is found to cause harmful interference to other radio users, the Agency may require its use to be modified or suspended.
Common Base Station licensees should write to their appropriate licensing centre or:
RA2/Public Telecommunication Networks Section
Radiocommunications Agency,
Wyndham House
189 Marsh Wall
London
E14 9SX
Tel: 020 7211 0238
PMR (Standard) licensees should write to the appropriate local RA office. You can find the phone number and address of your RA local office by contacting the Agency's Enquiry Point on 020 7211 0211, alternatively the phone numbers and addresses of the Agency's Local Offices are listed on the information sheet RA 206 which is available from the Agency's Information and Library Service on 020 7211 0502/0505.
Applications for new PMR (Standard) licences with interconnect facilities should be forward to the appropriate local RA office or Central Licensing Unit at the Agency's HQ using form RA1. The request for telephone interconnect should be specified in the special facilities question on the RA1. The appropriate documentation as detailed above should accompany the application.
The use of all apparatus, PABX or otherwise, which is connected to the PSTN, is automatically licensed under the Telecommunications Act 1984 (Telecom Act).
Where such apparatus is also connected to radio apparatus, licences are required under both the Telecom Act and the Wireless Telegraphy Acts 1949 (WT Act) Section 1.1 and 1998.
The Telecom Act licence covering interconnect operation is titled:-
"The class licence for the running of private mobile radio systems, radiopaging systems and automatic location systems for the provision of services to third parties granted by the Secretary of State for Trade and Industry under Section 7 of the Telecommunications Act 1984".
This licence is called a self provision licence (SPL). It is not held by the licensee who is covered automatically by the existence of the class licence.
If there is any doubt as to whether or not a Telecom Act licence is needed to operate a system, the applicant is advised to contact the Office of Telecommunications (OFTEL) at the following address:
OFTEL
50 Ludgate Hill
London EC4M 7JJ
Tel: 020 7634 8700
For further information on telephone interconnect or radio matters in general, contact the Agency's Enquiry Point on 020 7211 0211, or Public Telecommunnication Networks Section or your local RA office.
website: www.radio.gov.uk
| RA 222 (Rev 2) May 1999 |
