"Hello, can I speak to the president?" is not an off-the-cuff request an operator is ever likely to hear from a world leader.
By the time the initial pleasantries are exchanged between heads of state, the groundwork will have been done behind the scenes by the leaders' respective staff.
"When there is an established relationship between two countries, it might be as simple as one situation room calling its counterpoint and saying my head of state wants to speak to yours," says Stephen Yates, who worked as deputy national security adviser to former US Vice-President Dick Cheney.
When countries are in less frequent contact, an ambassador may make the first formal request on their leader's behalf. They will set out the proposed agenda and reasons for the call and, if agreed, the reciprocal team would then work it into busy schedules.
World leaders are typically well briefed before speaking to each other.
In the US, the president is given a dossier from the National Security Council (NSC), the principal US advisory body on national security and foreign policy.
If it is a simple courtesy call, the information provided may be basic, including details on who initiated contact, and two or three recommended talking points. There may also be some need-to-know personal information, such as a reminder to ask after a sick husband or wife.
US presidential translators will have passed security clearances, background checks and even sat polygraph tests, before they become privy to sensitive information involved in high-level diplomacy.
"There are no novices that work at the presidential level," says Mr Hendzel. "It takes a great deal of time for an interpreter to reach this stage. They are also experts in the subject matter, and they know getting a form of address wrong can be a deal breaker."
"It's apples and oranges when you are comparing transitional calls by a president-elect to those of a head of state in the Oval Office," says Mr Yates.
Once Mr Trump is in the hot seat, all his calls will be highly secure and heavily vetted.
"The president will feel like he has just picked up the phone, like any other call, but the call will have been through multiple checks to ensure its fidelity," says Mr Yates.
Sometimes this vetting process can be so tight, the wrong people get cut off. "I am fighting w[ith] the WH operator who doesn't believe I am who I say," wrote exasperated Secretary of State Hillary Clinton in a 2010 email.