A handheld battery-powered telecommunications test instrument for monitoring the status of a pair of wires. A tone-generating circuit generates a tone signal in response to the user manually selecting operation in a tone-generating mode. The instrument monitors the pair of wires to determine whether an on-hook, off-hook or ringing signal is present on the wires, and if present, generates an interrupt control signal through a microprocessor. Logic circuitry connected to the microprocessor results in connecting and disconnecting the tone-generating circuit and the pair of wires to selectively apply the tone signal to the wires. In response to the control signal and the user selecting the tone-generating mode, the microprocessor connects the tone-generation circuit to the pair of wires if no control signal is generated, and disconnects the tone-generating circuit if the control signal is generated. The presence of the on-hook, off-hook and ringing signals on the pair of wires is determined by measuring the voltage between the pair of wires. A menu is generated by the microprocessor from which the user can select the frequency and amplitude for the tone signal.