Overview of Caller ID Standard and Market in Taiwan

Overview of Caller ID Standard and Market in Taiwan

Market Status

In 1999, Chunghwa Telecom, the state owned telephone carrier in Taiwan, had officially launched Caller ID service in Taiwan. By offering Caller ID service as part of the standard telephone package, Chunghwa Telecom is one of the first carriers to implement Caller ID on an existing network without additional charges. Since Caller ID features are traditionally considered a paid service, Chunghwa Telecom is raising the standard for what is considered basic telephone service.

Owing to the network compatibility issues, Type 1 Caller ID service is being offered in certain cities or areas only with number delivery. The incompatibility and limited service area leads to a problem of usability. Often, calls from outside the various service areas are reported as "Out Of Area". As a result, the performance of the current Caller ID Service is below some customers’ expectation and anticipation. The general feeling from various Caller ID device manufacturers is that the limited service areas are reducing the benefit of Caller ID and resulting in disappointed customers. As such, the demand for Caller ID devices from consumers is slowing from the initial surge.

Official Caller ID Standard

Taiwan has adopted both FSK and DTMF Caller ID transmission formats as per the ETSI Standard ETS 300-659-1. Depending on the capabilities of the central office switch serving a given area, the Caller ID data is transmitted by means of a FSK modulated carrier or by sending DTMF digits. The official Caller ID document 0003-0 was released on Nov. 22, 1999 by the Directorate General of Telecommunications, Republic Of China. 

FSK Caller ID Transmission

The FSK based Caller ID transmission method uses a Dual Tone Alerting Signal (DTAS) to inform the Terminal Equipment (TE) of an incoming Caller ID message. The Caller ID message is sent using a V.23 FSK signal, which is followed by one or more power ringing cycles. The following figure shows the sequence of events.

The timing limits are defined as follows:




Silence time from DTAS to start of FSK data

>=45 ms and <=500 ms


Delay from end of FSK data transmission to first ring

>=200 ms and <=500 ms


Delay from the end of DTAS where the TE must be ready to receive the FSK data

=< 45 ms


Delay from the end of the FSK data where the TE must reject further data

=< 150 ms


The Reason of Number Absence parameter type is slightly modified from the ETSI specification. The following list shows the representations used:

Reason of Number Absence



Coin/Public Phone Call


International Call


Out of Area Call


Private Call


DTMF Caller ID Transmission

The DTMF based Caller ID transmission method sends a series of DTMF digits prior to the first ringing cycle. As shown in the following figure, the calling number is sent following a "start" digit and ends when the "stop" digit is detected.



The timing limits are defined as follows:





Pause for the central office switch to connect the DTMF sender to the voice path

50 ms ~ 400 ms


Duration of the DTMF digits

>=50 ms


Inter-digit pause

>=50 ms


Delay from the end of the last DTMF digit to the start of 1st ringing cycle

>=150 ms and <=700 ms


Time required to send all the DTMF digits

=< 3000 ms


Return to quiescent state after receiving the DTMF stop digit "C"

=< 150 ms

The transfer of number information is to be regarded as completed when one of the following criteria are met:

1. The DTMF digit "C" (stop code) is received;

2. Ringing signal is detected;

3. After receipt of a DTMF digit the DTMF pause condition is present for more than 1 second.

At least the criteria 2 and 3 shall be supported by the TE, as these criteria will guarantee in both normal and abnormal number information transfer procedures, that the NIT state is left before, or as soon as possible, the line entering an off-hook loop condition.


Caller ID Testing and Approval Authorities

Caller ID Terminal equipment are subject to formal approval before they are permitted to be sold to the general public in Taiwan. For further information, please contact the following Official Approval Authorities:

ETC (Electronics Testing Center,Taiwan)
Tel : +886-3-328-0026
Fax: +886-3-328-3928
Contact: S.C. Chen
E-mail: johnson@etc.org.tw

TL (Telecommunication Laboratories Chunghwa Telecom Co., Ltd.)
Tel: +886-2-2326-2470
Fax: +886-3-424-5556
Contact: Jin Chuan Chan
E-mail: wxmc@ms7.hinet.net