Lines & Numbers

  • Digital ISDN lines, or Analogue
  • New SIP trunks, via broadband
  • Local area, remote area or non-geographic numbers
  • How many numbers do you need?
  • Direct dial numbers to extensions or groups
  • Multi-company needs
  • Links to remote offices and/or homeworkers
  • Traffic statistics


Previously business users were offered a comparatively simple choice between using digital ISDN or analogue phone lines for their business. In either case, multiple calls could (can) be catered for by ordering multiple ISDN channels, or multiple analogue lines - with all associated phone numbers arranged to cover all lines together.


ISDN lines come in two varieties, depending upon the number of channels likely to be needed by a business. For smaller business needs, ISDN 2e lines provide two channels, where each channel is equivalent to a single analogue line, allowing one incoming or outgoing call at a time. Larger numbers of calls are allowed by adding more ISDN 2e circuits, up to typically 3 or 4 lines, above which a single ISDN30 line is used, with anything from 8 to 30 channels activated. In all cases one incurs a monthly rental charge per activated channel.


ISDN lines generally offer superior call quality, and the often critical advantage of allowing multiple numbers to be used over all channels. Multiple DDI (Direct Dial Inward) numbers may be used for many different purposes, but typically for direct dial access to individual extensions or department groups, without need for prior reception and internal call transfer. They may also be used for automatic internal routing of calls to different businesses within the premises - or for internal indication to the call taker that some special number has been called, such as a promotion number, or that the call has originated in some remote area. Use of 20 to 30 numbers by even a comparatively small business in not uncommon. New numbers can usually be added in blocks of 10 at any time, at modest set-up and ongoing monthly rental costs.


Analogue lines are generally supplied with only a single number for each line, or over a group of such lines, giving less flexibility in their use within a business. Monthly rental costs for each analogue line and each ISDN channel are usually the same, with identical call costs for outgoing calls over either line type.

Both new ISDN and new analogue lines are assigned one or more local area numbers, which need a local area dialling code followed by typically 5 or 6 digits. These numbers are known as geographic numbers and may be of the form 02392 552855, as for our business number. Historically BT and other providers also offered a range of special rate non-geographic numbers, including 0800 ('free-phone'), 0845 ('local rate'), 0870 ('business rate') or 090 series ('premium rate') numbers, which could be called from anywhere within the UK, using a landline phone, for the same given call cost. Calls to these non-geographic numbers from a mobile phone are likely to be more expensive, including to 0800 series numbers, for which all calls will be charged.

As the cost of calls to local area and other national numbers has dropped, there is frequently less need for such special numbers, so opening the comparatively recent release of a new set of 03XXX series national rate, non-geographic numbers which incur comparatively modest call charges, whether from landline or mobile phones. Each such number, when ordered, can have all associated calls routed to a specified geographic number, with time-of-day alternatives sometimes available for weekend or night-time calls.


A totally new range of business telephone lines has recently been introduced, with connection over ADSL broadband circuits. These are mostly known as SIP Trunks, although different types are also available. They are intended as an alternative to analogue or ISDN lines, and often provide a more cost effective service than that offered by the older services. Provided that a suitable broadband service is available, new SIP trunks can often be set-up and activated far more quickly than the installation time for either new analogue or ISDN lines. They also often offer a huge range of add-on benefits, such as very simple disaster recovery changes, number flexibility, off site call recording etc. 


Please call Hi-Port Telecom for further details.