The jacks on the front and sides of the UP5, UR92, UR91, UR90, and LNRP front panels are Throttle Jacks and should only be used for connecting throttles to LocoNet. They should not be used to connect to other LocoNet devices.
The jacks on the back of these units are LocoNet Jacks that are used for connecting LocoNet devices to the network.
Technically speaking! These units were designed to have the FRONT jack's second Railsync differential signal run as a diode-or'ed power source (for throttles). This means that some cable orientations and power loads could cause unexpected operations in downstream LocoNet devices connected through the Throttle Jacks. Boosters, BDL16x, DS64, SE8x and LNRP are examples of units that must be plugged in through LocoNet Jacks on the rear of the panels because they use DCC packets from the LocoNet cable Railsync lines.