HSL (Hay Systems Ltd) is an independent mobile network operator and provider of mobile services to organisations and individuals around the world. HSL's focus is on quality and reliability of service to its customers through the strong technical emphasis of the company.

As an operator of its own GSM network, HSL is involved in the development of GSM mobile network infrastructure and is recognised for consistently delivering superior and technically advanced solutions including SMS gateway services and mobile network services.

HSL was formed in 1999 and has evolved into a mobile operator having originally been established as an SMS gateway service provider. SMS remains a core activity through the Mobile Messaging division of the company. However, due to the growth and development of technical capabilities HSL now operates mobile network services and has the capability to self-provide certain aspects of its own mobile network including SMSC platforms and GSM femtocell base stations through the Mobile Networks division of HSL.

HSL's head office is located on the outskirts of Edinburgh, Scotland. In addition to our Scottish base we also have sales offices in London, Paris, Frankfurt, Dubai and Wellington serving the needs of our global client base.

HSL are members/participants in 3GPP, ETSI, Federation of Communication Services (FCS), Otelo, MNP OSG and the Femto Forum.