Synchrotech's P-series line of PCMCIA SRAM PC Cards are designed with the dual back-up battery system featuring a replaceable but non-rechargeable 3 V lithium battery (primary battery) and an on-board rechargeable but non-replaceable battery (secondary battery) for data retention. This design allows replacement of primary battery without data loss for approximately 20 minutes. These replaceable battery models have access times of 200 ns and a broad range of PCMCIA SRAM PC Card capacities. The cards are compatible with nearly all known PCMCIA SRAM PC Card applications and feature a write protect switch for preventing inadvertent erasure. The card's rigid stainless steel and plastic construction withstands harsh environmental conditions.