A wireless telecommunications system supports a DRX operating mode for communications between a base station and terminal device, which includes a regular repeating cycle of DRX inactive periods when the terminal device monitors a downlink channel from the base station and DRX active periods when the terminal device enters a power-saving mode not monitoring the downlink channel. The terminal device transmits uplink signaling, triggering subsequent downlink signaling, that may include acknowledgement signalling for a previous downlink transmission or an uplink transmission resources request. The base station receives the uplink signalling, determines time of an upcoming DRX inactive period for the terminal device, and delays transmitting downlink signalling responding to the uplink signalling until the upcoming DRX inactive period. The terminal device enters the power saving mode after transmitting the uplink signalling and exits the power saving mode for the DRX inactive period to monitor the downlink channel for downlink signalling.