New Motorola Desk Microphone RMN5068 replaces HMN3000B

The main problem with the new RMN5068A Desk microphone that replaced the HMN3000 is that it works with the Motorola mobiles but doesn't work with dispatch solutions such as the MC series desksets and the Commandstar lite console all of which are manufactured by CML. What we discovered is the mic DC voltage supplied by the mobiles is around 5 to 7 volts. The mic dc that the CML products supplies is almost 12 volts. The HMN3000 tolerated the higher voltage without affecting the mike audio. The new RMN5068A can't tolerate that higher voltage and causes the mic amplifier circuit to go into distortion.

We have modified the new mic by bridging a 680 ohm resistor across mic high to mic low in the mic. The resistor drops the mic DC voltage allowing the RMN5068A to work with the CML products with great success. We presently have about 20 RMN5068a working on MC series desksets. This modification is not from Motorola so it is not sanctioned by them but works every time.

As some additional information on this microphone, you will notice that there is a multi position switch located inside the mic to allow the mic to be configured for different radios. (Monitor before transmit, separate grounds for PTT and mic low, etc.) You will find this info in no manual. If you call the System Support Center they will read you the functions of the various switch positions but they can not fax or email any documentation. I have included the switch functions in this email so you don't have to go through the same problem.


https://xpr5550.blogspot.ca/2015/11/motorola-rmn5050a-desktop-microphone.html