Sim tech wrote,
I think that the locking intercom trigger on the yoke is compulsory on British-registered aircraft. One of the sims I work on came over from the States; it didn't have the locking facility so we had to add it as part of the work required to get CAA approval for British crews to train on the device.
I can think of a British registered B747-400 Freighter crew that wishes it had locking intercom switches! The ones we operate do not have locking switches.