Abstract: A telephone call security system uses a long distance carrier access switch to prevent unauthorized access to the carrier by causing the switch control system to request a telephone identification serial number from the telephone and deny access if the serial number is not valid or if the number dialed is not an authorized number for the telephone whose serial number has been received. In addition, the system uses a coded query/response dialogue between the telephone and the switch control system for added security. The system may be implemented by modifying the carrier access switch control software and also includes a unique telephone and telephone resident control software.

Abstract: A transmission system develops a binary encoded data train having a message and a header preceding the message. The data train is applied to a carrier frequency to modulate the carrier using FSK techniques. The header includes synch signals, one or more address signals, a message length signal and control signals separating the above signals. One or more personal receivers receive the message if responsive to one of the address signals in the header. An address signal may address a unique personal receiver, a selected group of or all such personal receivers. Each receiver is sequentially activated and deactivated, being activated to detect a synch signal. If synch signals are detected, the receiver remains activated to determine if an address signal identifies such receiver to receive the message. A received message is stored digitally in a number of storage locations determined by the message length signal and may be selectively displayed in alphanumeric characters when convenient for the recipient.