This is a case about Dual-roles.

Engr. Solis is employed on a full-time basis by a radio broadcast equipment manufacturer as a sales representative. In addition, Solis performs consulting engineering services to organizations in the radio broadcast field, including analysis of their technical problems and, when required, recommendation of certain radio broadcast equipment as may be needed. Solis engineering reports to his clients are prepared in form for filling with National Telecommunications Commission. In some cases, Solis engineering reports recommend the use of broadcast equipment manufactured by his employer. May Solis ethically provide consulting services as described?

Who was his first employer? What is that employer's policy concerning employees working for another company?

Do the two companies know he is working for both of them?

I can see a ethical situation when his reports recommend the usage of the equipment his first employer makes. He could be accused of favoring his first company in the recommendations he makes to the other companies.

Conflict of interest is the term.

That being said, Mr. Solis should go to his primary company's policies on conflict of interest and how that company interprets that. Then talk to his Human Resource Personnel, or his supervisor.