| Business | Phone |
| Applied Communications & Tech 6324 Frostwork Row, Columbia 21044 | (301) 596-6230 |
| Ark Systems Inc 9176 Red Branch Rd # B, Columbia 21045 | (410) 995-1220 |
| Questron Inc 8310 Guilford Rd # B, Columbia 21046 | (410) 720-5600 |
| S R Aquino Electric & Alarm Co Columbia 21046 | (410) 381-3500 |
| Vector Security 9800 Patuxent Woods Dr # B, Columbia 21046 | (410) 655-7474 |