Abstract: A ringer employs a low-cost miniature transducer, having a reverberant cavity, mounted in a cylindrical housing which has a second reverberant cavity in front of the miniature transducer. A very large acoustic output power is achieved when the ringer is employed in known cordless telephones, using the conventional available 3.9 volts battery. The ringer, due to its small relative size, may fit in the limited space inside a cordless telephone portable unit without costly tooling modifications. It is also suited for other uses, including for employment in compact one-piece telephones. The ringer is substantially more compact, louder in sound level, more pleasant sounding than known devices, and operates from a substantially lower DC voltage source.

Abstract: A telephone security system particularly for use with cordless telephone, operates to prevent the base station of the system from being accessed by an unauthorized user.Preselected digits are set by means of switches. In order to receive a dial tone, the correct digits as selected by the switches must be dialed. The security system operates to compare the dialed digits with those digits set by the switches. If a favorable comparison is had, the security device then connects the telephone line to the base station and allows dial tone to be transmitted to thereby enable a call to be implemented by the user.