| 摘要 |
A special services add-on specifically adapted for use in a dial pulse activated telephone switching office such as a step-by-step office to enable the addition of various modern features thereto, thereby extending the economic life of the office. The add-on is a stored program, processor based system that can be put into service on a line-by-line basis independent of subscriber line assignments. Among the special services provided by the add-on are incoming call alert, call conferencing, call forwarding, tone dialing, abbreviated dialing, instant recall, restricted calling, ringback, delayed ringback and ring disable. Various of the services are remotely controllable by the subscriber by dialing programming instructions to the add-on either from his own or another telephone subset.
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