What is calling number display?

Calling Number Display or caller ID allows telephone customers to identify the number from which an incoming call is made. Customers with Calling Number Display equipment can view the number of anyone who calls them unless that person has exercised the option of having their call blocked. They can also record the numbers of people whose calls were not answered.

Telstra introduced Calling Number Display for its fixed line and digital mobile customers in December 1997. CND is now available over the Telstra fixed network and Telstra, Optus and Vodaphone mobile networks, and for caller data shared across these networks.

Blocking of calls can be implemented through line blocking (blocking all calls from a particular line) or per call blocking (entering a four digit number which disables the transmission of calling line information for a single call). By dialling 1831 each time you make a call you will have that call blocked. By dialling 1832 silent line customers or people with blocked lines can send their number for an individual call. Telstra silent line customers receive automatic line blocking. Other customers need to contact Telstra to request line blocking otherwise their numbers will go to subscribers who have Calling Number Display equipment. You can block or unblock your line free of charge provided you do not change your option more than once every six months. Blocked calls are still disclosed to emergency services.

Businesses which have Calling Number Display can record numbers of incoming calls on a computer database and add this to the information they hold about customers and potential customers. They can use the information to develop personalised services for customers, for example recalling previous calls from the same customer or sending incoming calls to specific staff. Advertising by carriers has tended to place less emphasis on these business uses and to highlight the convenience of Calling Number Display for individual customers for weeding out nuisance calls and responding to call waiting .

What are the privacy issues?

Calling Number Display raises privacy concerns because:

• businesses can collect the numbers of callers without the callers realising and use this to build up customer profiles,
• businesses can use Calling Number Display to discriminate against customers by delaying or refusing to answer their calls,
• anonymous calls to government departments may not be quite as anonymous,
• employees’ locations can be checked when they call work,
• Calling Number Display works better for business and carriers if fewer people block their calls. Carriers favour a system whereby users have to opt out of having their calling line information sent automatically. They have few incentives for ensuring that blocking is 100% reliable.

• They must ensure a high level of public awareness as to how Calling Number Display operates so that individual consumers can make informed choice on how to use it.
• There are to be no charges for either line blocking or per call blocking, and it should be possible to send line information for individual calls from a blocked line without any extra charge.
• Carriers and service providers should be able to effectively deliver the required level of security to customers who choose to block their calls. The security of silent line customers must be maintained.
• There should be uniform means of blocking or unblocking calls over the telecommunications network as a whole. There should be one number that consumers can use to block calls irrespective of which carrier or service provider they use.