This is ment to be a upgrade version of Engineer PDA which while really good has a costly downside.
The PDA
The Explosive Sentry: This sentry where instead of shooting regular bullets; its shoots short-range explosive rounds similar to the Anti-Aircraft Cannon which it upgrades improving it distances. It cost 200 Metal to build.
The Repair Node: the Repair Node would periodically repair all nearby buildings before temporarily ceasing function in order to recharge; the recharge time is 15 Seconds. Its cost 200 Metal to Build.
The Advance Teleporter: These are just buff up teleporter that can teleport 2 people at a time. The entrance & exit cost 100 Metal.
This PDA while really good cost alot of Metal to build and repair buildings and you lose your dispenser. Its basically a glass cannon PDA and Buildings.