Abstract: An electronic control system for model railroads incorporates electronics which "arms" all railroad track switch turn-outs (here after referred to as "turn-outs") at once, selects and toggles the state of a specific turnout by the approach of a model train directly after arming, and "disarms" all the turnouts at once when the selected turnout has operated. A variation of this method is also applied to model railroad electric uncoupler track sections or automatic unloader track sections to arm, select, operate and then disarm any desired track section.

Abstract: Electronic circuits and methods are provided for remote control of a locomotive in a model railroad layout having an interruptible DC power supply coupled to the railroad track. The locomotive motor is isolated from the track so as to allow use of polarity reversals on the track power signal for controlling remote effects in the locomotive such as sound effects. An on-board electronic state generator is provided in the locomotive for maintaining one at a time of a predetermined set of states, at least one of the states having a corresponding remote effect associated therewith. Remote control signals such as a reverse in polarity of the DC track power signal are used to clock the state generator to a desired state, thereby permitting control of a plurality of remote effects using only the traditional DC power supply interface. The locomotive motor is controlled by a motor reverse unit so that the motor direction is controllable independently of the polarity of the DC power signal applied to the track.

Abstract: Electronic control circuits for model railroading including a reversing motor control circuit. An on-board electronic state machine indicates one at a time of a predetermined series of states including forward, neutral and reverse, and is clocked to the next state responsive to an interrupt in the track power signal. The circuit further includes reset means for resetting the state machine directly to a neutral state responsive to an interruption of the track power signal of extended duration. The state machine can be remotely programmed to reset to any desired one of the series of states in response to a track power signal interrupt. The unique reset state is useful for receiving various remote control signals without driving the motor.

Abstract: A model railroad cattle car sound effects system includes a speech synthesis circuit (FIG. 6) for "playing" selected cow voices stored as digital data in an EPROM (160). In a random mode of operation, a state generator (30) provides a pseudo-random count that is used to select among four different calm cow voices, one of which is silence. The resulting audio output is perceived as random contented cow sounds. A pendulum motion detector (FIG. 8) provides an indication of lateral motion of the system. An up/down motion counter (40) maintains a motion count reflecting the level of excitation of the system (and the cows). The motion counter increments responsive to motion, and decrements gradually in the absence of detected motion. A motion count of at least four invokes a triggered mode of operation, in which the counter output is used to select among four different excited cow voices. The resulting audio output imitates increasingly agitated cows as the motion count further increases.

Abstract: An improved circuit simulator interface permits a user to define one or more output parameters describing behavior of hierarchically-defined subcircuits of a circuit. The user defines each output parameter by a hierarchial expression including one or more primitive output parameters generated by a simulator when simulating the circuit or other user-defined output parameters describing behavior of subcircuits of the circuit. Once the circuit simulator has simulated the circuit and has generated the primitive output parameter values, the simulator interface responds to a user request to display the value of a selected user-defined output parameter by decomposing the hierarchical parameter expression defining the selected output parameter to an expression combining only primitive parameter values. The simulator interface then evaluates the decomposed expression using primitive parameter values generated by the simulator and displays the result.

Abstract: An electronic control system for model railroads incorporates a motor control unit, an electronic state generator that generates particular operating state signals and a remote control signal generator that multiplies the number of remote control effects that would be available from the remote control signals alone.

Abstract: An electronic control system for model railroads incoporates a motor control unit, an electronic state generator that generates particular operating state signals and a remote control signal generator that multiplies the number of remote control effects that would be available from the remote control signals alone.

Abstract: An analog signal multiplexer for differential signals comprises a plurality of channels, each channel having a pair of differential amplifiers forming an input stage for receiving a differential input signal and a pair of output transistors for forming an output stage producing a differential output signal. Each differential amplifier has a pair of emitter-coupled transistors, with each transistor having an additional emitter cross-coupled to the additional emitter of the opposite transistor of the other emitter-coupled pair. A plurality of current sources are provided to bias the emitter-coupled and emitter cross-coupled pairs. By selectively enabling the current sources, the input signals forming the differential input signal can be applied with normal polarity or inverted polarity to a respective transistor of the output stage to produce a normal or inverted differential output signal or to both transistors of the output stage to produce no differential output signal.

Abstract: A resonance compensated unity voltage gain amplifier comprises an input stage and an output stage connected in feedback to the input stage and a series resonance circuit for compensating for the resonance of the output and input stages created by the feedback. Reactance of the series resonance circuit is adjusted to be substantially zero at the resonant frequency of the amplifier. The resonance compensated amplifier is incorporated into a gain selectable amplifier. The resistance on the output stage of the amplifier across which the input voltage is applied via the output voltage may be selectively varied to change the current gain of the amplifier.

Abstract: A DC level shift circuit includes a differential amplifier with a level shift stage. The level shift stage has two portions for transmitting the input signals forming the differential signal through the level shift stage. A current source transmits the input signals through the level shift stage. Transistors with impedances substantially equal to the current source impedances are cross coupled to each input terminal. Each transistor senses a distortion signal produced by the current source impedance at one terminal and produces in response a correction signal. The correction signal is then transmitted to the other input terminal to be summed with the distortion signal there to pass the input signals through the level shift stage without distortion. The DC level shift stage is also responsive to another correction signal generated by a feedback control stage to control the common mode voltage of the amplifier.

Abstract: An impedance neutralization circuit produces correction currents to compensate for the effects of parasitic impedance on the output voltage of an amplifier. In the described embodiment, the neutralization circuit includes a pair of emitter followers, one coupled to the collector of each transistor of a common base amplifier for sensing the output voltage at each collector. A pair of transistors are coupled one to each emitter follower for applying the sensed voltage across a neutralizing impedance proportional to the parasitic impedance seen at the collector of the opposite transistor of the common base amplifier. The voltage applied across the neutralizing impedances produces a correction current. The correction current is summed with a distortion current of proportional amount but opposite sign produced by the output voltage applied across the parasitic impedance to produce a substantially error-free output voltage.

Abstract: A high-precision amplifier employs a feed-forward technique to provide a first order correction of amplifier distortion. A second amplifier is utilized to sense the base-to-emitter distortion of a main amplifier and develop an error output which is injected into an output node to provide cancellation of distortion from the output of the main amplifier. The feed-forward distortion-correction technique is particularly applicable to high-precision wideband differential amplifiers; however, the technique may be used in other amplifiers as well.

Abstract: A high-precision amplifier employs a feed-forward technique to provide a first order correction of amplifier distortion. A second amplifier is utilized to sense the base-to-emitter distortion of a main amplifier and develop an error output which is injected into an output node to provide cancellation of distortion from the output of the main amplifier. The feed-forward distortion-correction technique is particularly applicable to high-precision wideband differential amplifiers; however, the technique may be used in other amplifiers as well.