It's surprising how many alarm company owners don't appreciate the need for a proper sales contract. Questions that you have regarding what you are supposed to do and what rights you have under certain circumstances are almost always governed by your contract. Your obligations and rights in connection with the sale, design and installation of the alarm system should be covered by the sales contract.
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There are typically two principal issues regarding the sale. First, you want to be sure you will be paid, and second, you want to be sure your subscriber can't sue you and win. Let's start with what is absolutely not acceptable. A proposal. I don't care if the proposal is a form proposal that you purchased, or a letter proposal that you put together. Most "proposals" are written in such a way that it calls for the subscriber to sign an approval on the proposal, and as soon as that is done, the proposal becomes the sales contract. If you insist on using a proposal then it should state on its face that "this proposal is subject to subscriber signing alarm company's standard sales contract." Also, there is no need for the proposal to call for the subscriber's signature on the proposal. The proposal is your offer to enter into a formal contract and the only way for a subscriber to accept that offer is by signing your formal sales contract.
You don't have a formal sales contract? Well, get one; right now. If you are doing sales you need a sales contract. Only the sales contract will cover the design and installation of the system. It will provide for collection issues if you're not paid. It will contain protective provisions in the event your subscriber suffers a loss related to what the alarm was intended to detect against. If your subscriber does suffer a loss, unless the failure of the alarm company is easily determined (such as failure to call police when signal received) the complaint against you is likely to claim defective design and installation as part of the negligence. Only the sales contract will cover that. The monitoring contract and service contract will not cover the design and installation. You need protection for all the services you provide. Sales, monitoring and service are 3 separate relationships you have with the subscriber, and you need 3 separate contracts.