Logic level test probe with grated oscillator

Electronic circuit test equipment comprising a probe for sensing electrical signals from a circuit under test,

• detecting means connected for receiving said electrical signals from said probe and for detecting the level thereof,
• a first detected signal converting means coupled to said detecting means for being triggered in response to a variation in level of the output from said detecting means, a second detected signal converting means coupled to said first detected signal converting means for being triggered in response to a variation in level of the output from said first detected signal converting means,
• a first oscillator means for providing an output signal when the signal from said detecting means is at a predetermined high level, a second oscillator means for providing an output signal when the signal from said detecting means is at a predetermined low level,
• a first OR gate having a first input terminal coupled to said detecting means for receiving said predetermined high level signal, and having a second input terminal coupled to the output of one of said first and second detected signal converting means, a second OR gate having a first input terminal coupled to said detecting means for receiving said predetermined low level signal, and having a second input coupled to the output of either of said first and second detected signal converting means,
• a first AND gate having a first input coupled to the output of said first OR gate and a second input coupled to said first oscillator means, a second AND gate having a first input coupled to the output of said second OR gate, and a second input coupled to said second oscillator means,
• a third OR gate having first and second inputs coupled respectively to the outputs of said first and second AND gates, a third AND gate having first and second inputs coupled respectively to the output of said third OR gate and the output of either of said first or second detected signal converting means, and
• electroacoustic transducer means which is driven by said third AND gate means, whereby a plurality of electrical conditions in the circuit under test can be converted into a plurality of tones of different frequencies audible to an operator.

Logic level test equipment comprising a probe for sensing electrical signals from a circuit under test,

• detecting means connected for receiving said electrical signals from said probe and for detecting the level thereof and for providing predetermined high and low level output signals in response to said electrical signal, a first detected signal converting means coupled to said detecting means for being triggered in response to a variation in level of the output from said detecting means, a second detected signal converting means for being triggered in response to a variation in level of the output from said first detected signal converting means,
• a switching circuit having inputs coupled to said detecting means and to said first and second detected signal converting means, said switching circuit having an output for providing variations in voltage in response to signals at said inputs thereof,
• oscillator means having an input coupled to said switching circuit output for providing an output signal which varies in frequency in response to said variations in output voltage from said switching circuit,
• And gate means having an output, a first input coupled to said oscillator means, and a second input coupled to said detecting means for coupling said oscillator means output to said AND gate means output in response to the presence of signals detected by said detecting means, and
• electroacoustic transducer means connected for being driven by said AND gate means, whereby a plurality of electrical conditions in the circuit under test can be converted into a plurality of the tones of different audible frequencies.

Logic level test equipment comprising:

• a probe for sensing electrical signals in a circuit under test,
• a probe body having a head portion and having said probe mounted at said head portion,
• detecting means coupled to said probe and including a first stage for detecting electrical signals of a predetermined first level, first illumination means connected to the output of said first level signal detecting stage, a second stage for detecting electrical signals of a predetermined second level, and second illumination means connected to the output of said second level signal detecting stage for emitting light having color of wavelength different from that of said first illumination means, said first and second illumination means being mounted at said head portion of said probe body,
• manual switch means mounted on said probe body and coupled to said first and second illumination means for operation to cause both said illumination means to emit light independently of said first and second detecting means signals,
• gate means having an output and having first and second inputs, wherein said first input is coupled selectively to one of said first and second stages of said detecting means,
• oscillator means having an output coupled to said second input of said gate means for providing an audio frequency signal for coupling through to said gate means output when said signal from said detecting means is applied to said first gate means input, and
• electroacoustic transducer means coupled to said gate means output for converting said audio signal into an audible tone.