초록 ▼

Remote telephone coder 10R and local telephone coder 10L provide coding and decoding for voice communication between remote telephone set 11R and local telephone set 11L through telephone line 12. An eavesdropper listening in on a listening device such as remote extension telephone 14R or local exte

Remote telephone coder 10R and local telephone coder 10L provide coding and decoding for voice communication between remote telephone set 11R and local telephone set 11L through telephone line 12. An eavesdropper listening in on a listening device such as remote extension telephone 14R or local extension telephone 14L hears normal "in-the-clear" conversation (uncoded transmissions) when both of the telephone coders are in the normal mode. However, when both of telephone coders 10R and 10L are in the code mode, the extension eavesdropper using an extension telephone or other unauthorized listening device 14 (shown in phantom) hears only coded transmissions. Further, a remote eavesdropper on remote extension telephone set (main portion 17M with hand portion 17H) employing remote extension coder 16R is also excluded from the coded transmissions between remote telephone coder 10R and local telephone coder 10L.

대표청구항 ▼

[ I claim as my invention:] [31.] A coder method of enabling encoding and decoding communications between a local telephone and a remote telephone and locking out any extension telephones, comprising:providing a local coder in a normal mode of operation during which out-going communications from the

[ I claim as my invention:] [31.] A coder method of enabling encoding and decoding communications between a local telephone and a remote telephone and locking out any extension telephones, comprising:providing a local coder in a normal mode of operation during which out-going communications from the local coder are not encoded and in-coming communications to the local coder are not decoded;advancing the local coder from the normal mode of operation to a wait mode of operation during which the local coder listens for an in-coming wait signal from the remote coder;opening a send window in the local coder to the remote coder during the wait mode;sending an out-going wait signal to the remote coder during the send window indicating that the local coder has advanced to the wait mode;closing the send window during the wait mode;advancing the local coder from the wait mode of operation to a code mode of operation during which the local coder and the remote coder are enabled to encode out-going communications and to decode in-coming communications, and during which any extension coders are prevented from the encoding and decoding;encoding out-going communications from the local coder to the remote coder during the code mode; anddecoding in-coming communications to the local coder from the remote coder during the code mode.