Everyone loves this mic but, some have problems with poorly grounded or high power mobiles (or both).  They tend to squeal in these types of vehicles.

They have worked great on all base stations tried.

Echo adjustment in the front, Volume and Talkback controls in the Back (inside)

Sensitivity: -42 dB at 1,000 Hz
Impedance: 3 K ohm and less at 100 Hz
Frequency Response: 150-3,500 Hz
Echo Frequency Response: 200-3,000 Hz
Battery: DC 9V
Mic element: Omni Directional electret condenser type.
Front Slide control Controls the amount of echo.
Dual Inside controls control the gain and echo speed.

Click for larger image

Unfortunately this microphone tends to have excessive RF interference and squeals just too often. Sometimes it works great for a well grounded station, sometimes it didn't for "less grounded" individuals and we just couldn't accept any more warranty claims due to this problem. We decided to no longer carry this product.

We are going exclusively with the RF Limited products, like the EC2018XTR. It provides higher RF immunity, higher reliability, better sound and exceptional noise cancelling ability (great for Talk Back)