The standard unit fitted to SAR aircraft at Bristow is the P&G CVFDR with the following spec:
1 hour three channel recorded voice (PIL/COPIL/AREA MIC)
5 hours recorded data (128 words/sec ARINC 573)
Their system for acquiring data is the BAE Systems IHUMS.
Standard UK aircraft have a requirement for 8 hours previous data retention, but IHUMS aircraft have an exemption for this at the moment as extra data is recorded on a data card to supplement the 5 hour tape data in the CVFDR.
Mandatory params for heavy aircraft are 30, but the lighter aircraft only require 15 to be recorded.
In the future (2003/5 onwards) you will see the regulations being updated as new requirements come in, including the ability of the recorder to function for at least 10 mins after a crash, with the CB pulled. The new recorders will have battery packs either built-in or added as a back-pack type device.