Solving $$ \frac{a_{1} X+b_{1}Y+c_{1}}{\sqrt{a_{1}^{2}+b_{1}^{2}}} =\pm \frac{a_{2} X+b_{2}Y+c_{2}}{\sqrt{a_{2}^{2}+b_{2}^{2}}} =\pm \frac{a_{3} X+b_{3}Y+c_{3}}{\sqrt{a_{3}^{2}+b_{3}^{2}}} $$
gives one in-centre and three ex-centres.
Solving $$ \frac{a_{1} X+b_{1}Y+c_{1}}{\sqrt{a_{1}^{2}+b_{1}^{2}}} =\pm \frac{a_{2} X+b_{2}Y+c_{2}}{\sqrt{a_{2}^{2}+b_{2}^{2}}} =\pm \frac{a_{3} X+b_{3}Y+c_{3}}{\sqrt{a_{3}^{2}+b_{3}^{2}}} $$
gives one in-centre and three ex-centres.