PTT Telecom has started a campaign to promote Operator Services, like Collect Call and Phone Card calls. The PTT Telecom Phone Card is marketed under the name of Scopecard. As in other countries, operator services are expensive, mainly because of the high costs of the personnel. Thus, it is obvious that Telecom is looking for ways in which these services can be automated.
One simple way of automating Phone Card calls is to connect customers with an IVR platform that handles the recognition of the card number, the PIN code and the number to be dialled via DTMF; this is how a large proportion of domestic calls are automated. However, few operators offer the capability to connect toll-free lines to an IVR application in another country. Also, in many of the countries where PTT Telecom customers spend their vacation rotary dial phones still form the large majority. Thus, large scale automation of card services implies the deployment of ASR. The same goes for automatic collect calls, of course.
For applications like automated card services it is not enough to have a recogniser that can handle isolated or connected digits in abstracto. For the real-world performance of the application a solid knowledge of the way in which customers pronounce card and phone numbers is at least as important, since that knowledge can be exploited in designing application specific language models. POLYPHONE has provided us with a rich source of information about the way in which Dutch people express these numbers.
Two items in POLYPHONE that are related to telephone numbers were analysed. The first pertains to numbers read from the response sheet. All these numbers were printed in the same format, i.e. area code, dash, subscriber number (e.g. 020-5252183). The second item consists of answers to the question Please, say a familiar telephone number. In discussing the results we will use the term digit for the words zero, one, ..., nine; the term number will denote numbers between 10 and 99.
Presently, the Dutch PTT's number plan has two groups of area codes, one comprising three digits (like 020 in the example above) and one comprising five digits (e.g. 08894). Subscriber numbers can have four to seven digits. Because transliteration does not include intonation markers, it is not possible to discriminate between three and five digit area codes. We doubt whether the transliterators would have been able to parse all answers to the request to give a familiar number correctly.
The format of the read numbers is quite different from the format of spontaneously produced familiar numbers: in read numbers the proportion of digits is much larger than in spontaneously pronounced numbers. It is also worth mentioning that 18% of the read and 23% of the spontaneous numbers contain extra sounds, far more often preceding the number than following it.
POLYPHONE provides similar information about the way in which long card
numbers and shorter PINs are pronounced. At the time of this writing these
expressions are still under analysis.