| Business | Phone |
| Control Instruments 6915 Mullins Dr, Houston 77081 | (713) 667-5067 |
| Cordyne Inc 9820 Drysdale Ln, Houston 77041 | (713) 460-5151 |
| Electronic Measurement Co 9120 Freeland St, Houston 77075 | (713) 944-0007 |
| Katy Instruments Co 16514 Park Row, Houston 77084 | (281) 492-7817 |