Aibo, Sony's entertainment robot dog, is getting cheaper to own. The company has unveiled a number of new versions of the electronic dog that offer improvements on the previous models and sport lower price tags.

From the outside, the most striking difference between the new and old models comes with the ERS-31L, which is based on the Latte and Macaron models that Sony put on sale last year but designed to look like a bulldog or pug, according to Sony. The original versions were fashioned after bear cubs.

With the ERS-31L, the price has also been reduced to £375 in Japan and £410 in North America. That compares with the present UK price for Latte and Macaron of £720.

New versions of Latte and Macaron, the ERS-311B and 312B, are also going on sale and have added Bluetooth support. A further new version, the ERS-311B/X has additional suede coating on top of the plastic casing.

Tokyo's Sony is also taking the opportunity to update its ERS-210A and 220A models with a faster processor that now runs at 384MHz, which is double the speed of the previous models. The updated versions will cost £807 and £968 respectively when they go on sale later this month in Japan and the US.

The new models come on the market three years after Sony first put Aibo on sale. Hailed at the time as the world's first entertainment robot, Aibo has sold over 100,000 units although interest from consumers has begun to wane recently.

In addition to the new hardware, the company has also begun publishing details of Aibo's system architecture on the internet in an attempt to get developers to work on independent software for Aibo and generate more interest in the products.

UK price cuts and launch dates have yet to be announced.