The present invention relates to a central vacuum power unit comprising in combination a canister, a chamber for collecting debris, a first plate, a second plate, a third plate, a duct, a motor-fan assembly, a filter, and a first baffle. The passive transponder circuits are selectively coupled to receive power from the antenna and provide a coded response identifying a key in response to key activation. Furthermore, the portable keying device securely reprograms the encryption key in the electronic terminal without having to dismantle the terminal, deactivate any anti-tampering features, or re-bond the terminal.