After programming, the following messages are displayed after
connecting a headset:
OK - no errors detected
Mic Open - microphone is disconnected, bad mic or
disconnected cable or connector wiring
Mic Shorted - microphone resistance is less than 2
ohms, likely shorted cable or connector
Mic Wrong - not the expected microphone type
Mic Ohms Bad - dynamic microphone ohms deviates
more than +/-30% from expected
Mic Current Bad - electret microphone current
deviates more than +/-70% from expected
(note - polarized electret mics vary widely and
may produce false errors in preset modes)
Mic Unknown - cannot determine microphone type
Spkr Open - speaker is disconnected, likely
disconnected cable or connector wiring
Spkr Shorted - speaker resistance is less than 2
ohms, likely shorted cable or connector
Spkr Ohms Bad - speaker resistance deviates more
than +/-20% from expected
(note - if headset has a volume control make sure
it is all the way up)
One Spkr Bad - speaker resistance is twice the expected value,
likely one speaker bad or disconnected
Lines Shorted - both speaker and microphone read less than 2
ohms, likely bad cable or connector
Lines Bad - one line shorted, one line open, likely bad cable or
connector
Mic & Spkr Bad - some other error involving both the microphone
and speakers
The unit beeps if the value deviates too much from the
programmed values. The programmed values are saved in
internal memory permanently until programmed again. When
switching to a preset, the display briefly shows the values pro
rammed for that preset.
When testing headsets with a volume control, turn the headset’s
volume control all the way up or the tester will add the volume
control resistance to the displayed reading.
It is normal for the current of type P microphones to vary widely
over time and in response to sound. Type P microphones require
that the + and - wires be connected correctly or they will read
UNKN.
The unit is not designed for carbon-type microphones. They
should detect as high impedance dynamic and the measure-
ment bias might permit some level of testing, but the readings
and the microphone output level and quality will vary widely.
The measured speaker ohms will fluctuate somewhat in
response to loud audio signals.
Higher impedance headsets will have less speaker output
volume; adjust the volume control as needed.
The output signal becomes slightly distorted with increased
microphone sound level, this is intentional and helps
differentiate the speaker signal from the operator’s natural
voice.
This unit measures DC resistance, not the true AC impedance.
Any electronics between the tester and the speaker or
microphone (transformers, capacitors, etc) will result in
incorrect measurement. Typically the DC resistance will be about
5%-15% less than the actual AC impedance at 1Khz, and
produce the same reading (within tolerance) as would be
obtained using a common multimeter. If true AC impedance
measurement is required then a custom adapter can be
devised.
CONNECTOR SPECIFICATIONS
CThe 13-pin side connector permits connecting adapters for
interfacing to different headset connectors and test leads for
testing individual microphone and speaker elements. The unit
comes with an adapter for headsets that use a common 4-pin
NEXUS-type connector, and a standard U173/U pin-type
connector for testing microphones. Adapters for other types of
connectors can be devised as needed, contact us for assistance.
In addition to speaker and microphone lines, the connector also
includes power and ground connections for powering
low-current external circuitry, extra audio inputs for connecting a
music player or other audio source, and connections for
interfacing with the headset tester’s processor for reprogram-
ming and other custom uses. The stock processor code for the
unit does not support user-level programming, rather these lines
make it possible to deliver code updates in the form of an
adapter and so that custom adapters can reprogram the
processor with the needed protocol.
User-constructed adapters should only connect to the microphone
and speaker lines, the audio input lines, and must draw no more
than 20ma from the +5V power line. Do Not make any
connections to the processor lines. Damage caused by improper
adapters is not covered under warranty!
The auxiliary audio input lines have an input
impedance of about 10K and are designed for signal levels of
about 1 to 2 volts RMS (the typical output level of a music
player). The signal is mixed with the microphone preamp signal
before the volume control.
The connector pins are as follows:
Pin 1 - headset micr
Pin 2 - headset microphone - (ground)
Pin 3 - headset speaker - (ground)
Pin 4 - headset s
Pin 5 - aux audio input 1
Pin 6 - aux audio input 2
Pin 7 - aux audio ground
Pin 8 - 5V power source (20ma maximum!)
Pin 9 - power ground
Pins 10-13 - processor lines, do not connect.