Calling for Help without Exacerbating the Situation
A system whereby a lone worker can quickly activate a duress code, without alerting an attacker, obviously helps to avoid exacerbating the situation.
The most effective way of doing this is to have a mobile phone or equivalent unit with an SOS facility or a speed-dial number connecting to an emergency response centre.
The emergency response centre will have up-to-date and accurate information about the lone workers and can direct the police to where they are.