Question: We recently got a Tempest 900MHz system. We keep having echo problems when the system is connected to one of the 4-wire ports on our RTS Adam frame. I've tried the manual null and auto null feature. I've turned on and offthe echo cancel feature to no avail. However the manual states if we areusing a four wire intercom that the null feature would not need to beused. They also recommend to keep the echo feature on. This is still enabled.  What could be causing this echo issue?
Answer:  The ECAN echo canceler feature in Tempest 2.0 systems is only active when the base station is placed into 2-wire intercom mode.  In 4-wire intercom mode this feature is not active, but we still recommend that the ECAN feature be left in active mode.  The Auto Null feature is only associated with the 2-wire PL channels (XLR IC connectors), it has no effect on the 4-wire (RJ45 IC connectors). 
Since the echo is only present on the beltpacks when the Tempest base station is plugged into the 4-wire port on the RTS Adam intercom frame check that the 4-wire port on the Adam frame doesn't have the audio looped back to itself, also determine if the Adam 4-wire port is a direct port or part of a party-line group which might include an IFB feed or telephone IFB feed. 
Another source of unwanted echo can be from open mics on the RTS Adam system user panels, determine if the Tempest beltpack users are close to an RTS panel with an open mic as the audio may be looping back from the Adam panel into the Tempest beltpack users open mic.  If this is the case the Tempest beltpack users headset mic gain may be an issue if the gain is set very high (say +30db or higher, typically with a CC-26 headset the mic gain should be set to +25 or lower).