Abstract: With Calling Number Identification (CNID) service, Frequency Shift Keying (FSK) data is sent over the telephone lines to the telephone service customer. A telephone subscriber may prevent their name/number from being transmitted to the party they are calling on a per call basis by dialing a prefix before they dial the desired number. The present invention allows for the automatic insertion/removal of that prefix in the number stream when the called party's number is dialed. This feature is accomplished by inserting a $ character into the dialing sequence. If the blocking feature is enabled, the $ is translated to the numeric sequence necessary to prevent the transmittal of one's telephone number. In the alternative, the $ is translated to a meaningless delimiter if the feature is disabled.