In answer to your question, the receiving/sending unit just plugs into the unit and the coach cigarette lighter socket. They do not have to be matched. They all run on the same frequency. If you're just missing the coach receiver and can find another one it will match the one on the unit. The system is inertia based. It's a great simple unit can be switched from vehicle to vehicle. Factory service is excellent. Mine is 8yrs old and malfunctioned, called brake buddy service, sent the unit to them they refurbished it with new air pump, power cord, reset digital read out for $75 including return postage took less than a week. Great service, saved $1400 on cost of buying a new replacement unit.