Digital input circuit for receiving digital input signals from a signal generator

A digital input circuit for receiving digital input signals of at least one signal generator, the digital input circuit comprising:

• a first subcircuit including:
• a first digital input to receive a first digital input signal;
• and a first threshold value element to determine a logic state of the first subcircuit, wherein the first subcircuit adopts a first state in response to the first digital input signal reaching or falling below a first lower threshold value and adopts a second state in response to the first digital input signal reaching or exceeding a first upper threshold value;
• a second subcircuit including:
• a second digital input to receive a second digital input signal;
• and a second threshold value element to determine a logic state of the second subcircuit, wherein the second subcircuit adopts the first state in response to the second digital input signal reaching or falling below a second lower threshold value and adopts the second state in response to the second digital input signal reaching or exceeding a second upper threshold value;
• and
• a combined test and current increasing apparatus to generate a driving signal such that a function test of both the first and second subcircuits is conducted simultaneously with the driving signal, and an input current of the first and second digital inputs is increased, wherein, in response to receiving the driving signal for testing, the first and second subcircuits are configured to internally lower levels of the first and second digital input signals, respectively, to correspond to the first state.