Connectivity
HP has implemented a modern USB Type-C port 3.1, but only Gen. 1, which is a typical USB 3.0 in terms of performance with another connector. DisplayPort or Thunderbolt are not supported by the port and you cannot use it to charge the device via USB Type-C. But there is no reason to moan, because you also get a full-size DisplayPort. This is rare since most notebooks - if at all - come with only a Mini-DisplayPort. The UltraSlim docking station, where you can put the 840 G3 on, comes with all the necessary ports including VGA d-Sub, DisplayPort or 4x USB 3.0.
Communication
Thanks to Ethernet (1 Gbps) and Dual-Band Wireless-AC 8260 as well as Bluetooth 4.1, you should not have any problems to establish wired or wireless connections. The Wi-Fi module supports Wireless Display, but the antennas do not seem to be as good as the recently reviewed Latitude E7470. The connection dropped at around 35 meters (~115 ft; outside the building) to the router (Fritz!Box 7490 AC). The E7470 still had a connection at 50 to 60 meters (~164 to 197 ft) in the same environment. An LTE modem is an optional extra, and the antennas are already integrated.
Security
Kensington Lock and fingerprint are the obvious security features of the EliteBook 840 G3. There are even more when we look at the BIOS; the software as well as the sensors. An accelerometer is supposed to park the read/write heads of the HDD when the device is dropped. However, this would only be useful if the test device had such an HDD. As per usual for EliteBooks, the BIOS (controlled with the mouse) has numerous possibilities to activate/deactivate ports and hardware as well as the configuration of individual components, such as the Turbo Boost settings of the processor, for instance. The item Security includes the setup of a DriveLock for the storage drive or performs a Secure Erase. TPM 1.2 can be activated just like a Power-On password.