Methods and Apparatus for Preventing a Third Party From Overhearing a Telephone Conversation

Methods and apparatus are provided for preventing a third party from listening to a conversation between at least two participants on a telephone. The telephone generates an audio stimulus signal that is presented through a secondary speaker. The audio stimulus signal may be, for example, pseudorandom noise or a cancellation signal. According to one aspect of the invention, the telephone ensures that the audio stimulus signal does not significantly impair the conversation for the at least two participants. To prevent the third party from listening to the local portion of the conversation, the audio stimulus signal is subtracted from the received signal prior to presenting the received signal to the user. To prevent the third party from listening to the remote portion of the conversation, the audio stimulus signal is subtracted from the received signal

Low-Power-Dissipation CMOS Oscillator Circuits with Capacitively Coupled Frequency Control

Methods and apparatus are disclosed for adjusting the frequency tuning range of an oscillator circuit. The oscillator circuit is comprised of at least two MOS devices; a first reactance connecting a drain electrode of a first MOS device to a gate electrode of a second MOS device and a second reactance connecting a drain electrode of the second MOS device to a gate electrode of the first MOS device; and a tank circuit connected to the source and drain electrodes. The first and second reactance may comprises a capacitor or a diode or a combination thereof. In addition, one or more resistors may optionally be connected between a gate electrode of at least one of the MOS device and a power source