U454B

The U454B has the following features including All functional blocks of a telephone appartus can be subscriberiine fed by an internal stabilized voltage of about 3.5 V DC;The microphone hybrid transformer U454B is replaced by an electronic circuit;High range of line feeding current;Input resistance independent of line current and sidetone suppression circuit;Built-in ear protection byearphone voltage limiter;Optional automatic equalization ofsending, receiving and sidetone reference equivalent up to 5 km subscriberline length.

The electronic speech circuit U 454 B is a linear integrated circuit applicable in telephone and other line fed terminal equipment. U454B replaces the common speech circuit with carbon microphone, hybrid transformer,sidetone equivalent and ear protection rectifiers.Two cheap electrodynamic transducers components necessary for amplification are used as microphone and earphone. The U 454 B contains all of signals and adaption to the line.The U454B is line fed. An integrated amplifier having 40 mW output power allows loudspeaking.Sending, receiving and sidetone suppression is optionally equalized from DC part of line current in such a way that the influence of a subscriber line loss or mismatch up to 5km line length is continuously compensated.Astabilized voltage ofabout 3.5 Vwhich is generated for the loudspeaker amplifier, is usable for further circuits in the set. There is no interaction between the 3.5 V and line voltage peaks orvalleys below 3.5 V.

The U454B described in this document are designed, developed and manufactured as contemplated for general use, including without limitation, ordinary industrial use, general office use, personal use, and household use, but are not designed, developed and manufactured as contemplated (1) for any use that includes fatal risks or dangers that, unless extremely high safety is secured, U454B could have a serious effect to the public, and could lead directly to death, personal injury, severe physical damage or other loss (i.e., nuclear reaction control in nuclear facility, aircraft flight control, air traffic control, mass transport control, medical life support system, missile launch control in weapon system), or (2) for any use where chance of failure is intolerable (i.e., submersible repeater and artificial satellite).