UM400a/UM450 v2.3

Improved battery telemetry signaling for slightly lower noise floor. Also corrected small audio level meter error in mode 3.

UM400a/UM450 v2.2

Reintroduced support for block 944 after version 2.0 removed it.

UM400a/UM450 v2.1 (Not Released)

Increased battery telemetry adjustment range and scaling, for faster and easier factory alignment and fewer component changes.

UM400a/UM450 v2.0

This version works with the new hardware design (both circuit boards changed) incorporating the National LMX2485 PLL. This version is also compatible with the newer 93LC86B EEPROM as well as the original 93LC86 EEPROM. Hardware using v1.x firmware must stay with v1.x firmware. Version 2.0 works on new hardware but is functionally identical to version 1.4.

UM400a/UM450 v1.4 (Not Releases)

Improved accuracy of compatibility mode 3. Performance in other modes unchanged.