What position should the ATC mode switch be in for territory transition?

The correct position for the ATC mode switch during territory transition is MCS (Manual Control System). This mode is specifically designed for situations where the automated control systems may not be applicable, allowing for manual operation. Transitioning between different territories often involves different signaling and operational protocols, which may not be compatible with automated systems. By setting the mode switch to MCS, operators can directly control the system, ensuring adaptability to the new territory's rules and requirements without risking miscommunication or signaling errors inherent in automated systems.

Choosing this mode allows for better situational awareness and operational safety while transitioning, which is crucial in environments where rail traffic and signaling systems may vary significantly.