Mechanical Installation, Speaker Dim Adjustment R157

Program Assignment – IFB Option (J4, J5, J16-J18)

Jumper J4 assigns PROGRAM A to two-wire CH 3 or four-wire CH B with interrupt during talk (IFB A). Jumper J5 assigns PROGRAM B to CH 4 with interrupt during talk (IFB B). (PROGRAM B is not used in four-wire mode.)

Jumpers J16, J17, and J18 assign the mono mix of both program inputs to the left headphone, right headphone, and speaker respectively. Program volume to the headphones and speaker is controlled by the PGM VOL control on the front panel.

See Table 2.2 for Jumper settings. See Figure 2.2 for locations of jumpers.

Balanced/Unbalanced Dynamic Microphone Selection (J24)

The MCE 325 may be used with headsets having either a balanced or unbalanced dynamic microphone. The MCE325 is pre-programmed for use with an unbalanced microphone by shorting J24 pins 2 and 3. For balanced microphones, remove the shorting jumper and reinstall it to short pins 1 and 2.

Headphone Sidetone Trimmer Adjustment (R37)

The headphone sidetone trimmer (R37) adjusts the loudness of your own voice heard in your headset when the microphone is on and the speaker is off. (It does not affect the actual level heard on the intercom lines.) This trimmer is preset so that your voice level in the headphones will be approximately ¾ of the intercom line level. To prevent feedback, this signal is automatically turned off when the external speaker is turned on with the SPKR ON switch.

Speaker Dim Adjustment (R157)

When an external speaker is used, switching the microphone on will cause the speaker level to attenuate. The level of attenuation may be adjusted with the speaker dim trimmer (R157). The minimum attenuation of 6 dB is preset at the factory (R157 fully clockwise). The range of adjustment is –6 dB to –40 dB.