Formula One's governing body has banned teams from sending drivers coded messages under a controversial clampdown on the use of radio communications from this weekend's Singapore Grand Prix.
The International Automobile Federation (FIA) issued a follow-up on Monday to a technical directive sent to teams last week in which it gave more information about what they could and could not do during a race weekend.
Banned items on the list, provided to the media by the FIA's Formula One delegate, included "any message that appears to be coded".
Teams were told that the use of pit boards for such messages was also banned.
Other no-nos were answering a direct technical question over the radio from a driver, such as "am I using the right torque map?", and information about the level of fuel saving needed.
- Acknowledgement that a driver message has been heard.
- Gaps to a competitor during a practice session or race.
- Tyre choice at the next pit stop and the number of laps a driver has done on a set of tyres during a race.
- Information about a competitor's likely race strategy.
The FIA moved to limit radio messages after concern that drivers were getting too much help from the pit wall and engineers.
The changes, after 13 of 19 races, has caused some concern about safety implications as well as the impact on fans, who will now hear less chat between drivers and their teams.
"This is a complex and controversial decision which will require a significant effort from the teams to understand how best we can work around it," Mercedes motorsport head Toto Wolff said of the new directive.