The 2049M Stethoscope consists of the 2049BDA amplifier, contact microphone/probe, special 2,000 ohm headset with ear hook and a carrying case. The system is designed primarily to detect conducted (seismic) sounds generated by mechanical clocks and trigger devices. The 2049BDA contains a low noise amplifier with switchable automatic gain control (AGC) and high/low pass filter. INPUT J1, accepts transducers (i.e. contact microphones) with impedances ranging from 10K to 500K ohms. The HEADSET J2 jack accepts headsets with a nominal impedance of 2,000 ohms (supplied with system) but will also accept headsets with impedances ranging from 600 to 50,000 ohms. The RECORDER J3 jack is designed to match the high impedance input of a tape recorder. This jack is normally connected to the AUXILIARY or AUX input of the recorder. If the recorder does not have an AUX jack, a 100/1 attenuator cable is required to prevent overloading.

OPERATION: Insert the contact microphone/probe into J1 and the headset supplied into J2. The headset is worn with the gray stethoscope tube UNDER the chin with the sound output holes facing slightly forward (30 degrees). Place the AGC-ON switch in the down or off position. Hold or place the contact microphone against the object under test (direct contact is mandatory). Rotate the VOLUME control slowly clockwise until the desired headset level is obtained. Select the FILTER switch position that gives optimum performance. If the probe is moved frequently or the surface is excessively noisy, turn on the AGC by placing that switch in the on or up position. Turn the VOLUME control to approximately 4 O'Clock. Once the AGC level has been set, it is no longer necessary to adjust the VOLUME control. Note that the volume automatically drops when the probe is moved and then returns to normal in 3 to 4 seconds.

The 2049BDA contains a single 9 volt battery which provides approximately 50 hours of "ON" time. Alkaline batteries are always preferred. As with any piece of sophisticated electronic equipment, remove the battery during periods of prolonged storage. When in the AGC mode, the headset level is controlled by the small potentiometer (variable resistor) located on the back portion of the circuit board. Use a small screwdriver to set this control to a higher or lower headset level.

Although designed primarily for bomb detection the 2049M has many, many applications. Some applications may be controlled by 18USC2512 or other federal, state or local laws. It is the owners responsibility to check for lawful use.


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