Microphones for vehicles

These are variously modified electret microphones with gooseneck and cardioid characteristics based on the GM-4 type, of which we are direct importers. The microphones have an integrated FET type transistor that amplifies the acoustic signal. Therefore, they require a power supply in the range of 1.5 V to 9 V (plus on the live shield wire). If no voltage is applied, the signal from the microphone is significantly weaker and is greatly distorted. The microphones are suitable for public passenger transport vehicles (we have been supplying them to transport companies since 1996).

The following figure shows the two frequency characteristics of the GM-4 microphone from the front (blue line) and from the rear (purple line). It shows that the rear direction is suppressed by about 10 dB.

The basic mechanical design of the microphone is shown in the following drawing. The microphones are supplied with an XLR connector length of 623 mm or shortened by the length of the connector, i.e. a length of 525 mm.

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Microphone design

GM-4U3WLM - Gooseneck electret microphone with 3 WAGO terminals with extended metal grommet

1. GM-4 electret microphone with modification (shortened and stripped of connector) and holder with metal grommet.

2. Double core shielded cable for microphone lead (EPIS microphone ground is connected to the microphone shield, the shield of the connecting cable is not connected).
3. 3 WAGO terminals and cable support located on the microphone holder.
4. Foam cover
5. For dashboard thickness 1.5 - 10 mm

GM-4 - Gooseneck electret microphone with XLR fork

1. Electret microphone body in aluminium housing
2. XLR connector type fork
3. Black gooseneck with a length of 480 mm
4. Foam cap

GM-4U3W - Gooseneck electret microphone with 3 WAGO terminals

1. Modified GM-4 gooseneck electret microphone and holder with PG 9 (shortened and stripped of connector).
2. Double core shielded cable for microphone lead (EPIS microphone ground is connected to microphone shield, shielding of connecting cable is not connected).
3. 3 WAGO terminals and cable support located on the microphone bracket.
4. Foam cover
5. For dashboard thickness 1.5 - 3 mm

GM-4U5W - Gooseneck electret microphone with 5 WAGO clamps

1. GM-4 gooseneck electret microphone with modification and holder with PG 9 (shortened and stripped of connector).
2. Double core shielded cable for microphone lead (EPIS microphone ground is connected to microphone shield, shield of connecting cable is not connected).
3. 5 WAGO terminals and cable bracket located on the microphone holder.
4. Foam cover
5. For dashboard thickness 1.5 - 3 mm

GM-4UD - Gooseneck electret microphone with loose wires 7 cm

1. GM-4 gooseneck electret microphone with modification and holder with PG 9 (shortened and stripped of connector).
2. Double core shielded cable for microphone lead (EPIS microphone ground is connected to microphone shield, shielding of connecting cable is not connected).
3. Foam cap

GM-4UK - Gooseneck electret microphone with 5.5 m lead cable

1. GM-4 electret microphone with PG 9 grommet.
2. Double-needle shielded cable 5.5 m long for microphone lead (microphone ground is connected to microphone shield, shield of connecting cable is not connected).
3. Foam cap