> ## Documentation Index > Fetch the complete documentation index at: https://www.vobiz.ai/docs/llms.txt > Use this file to discover all available pages before exploring further. # CPS - Buy Call-Initiation Throughput > Buy calls-per-second capacity in the Vobiz Console - what CPS controls, when to raise it, how the blocks-of-three pricing works, and how to preview the monthly cost before you purchase. **CPS (Calls Per Second)** is the maximum number of new call attempts your account can start in a single second - the top speed of your outbound dialling engine. It caps how fast calls go out, not how many can be live at once; that second limit is [Concurrency](/docs/platform/capacity/concurrency). ```text URL theme={null} https://console.vobiz.ai/app/profile/channel-subscriptions/cps ``` Open it from **Capacity → CPS** in the left sidebar. CPS page with a Purchase CPS card showing a quantity stepper in blocks of three, an estimated monthly cost, a pricing bracket table with units, price per unit and subtotal, and a Buy CPS button, beside a What is CPS explainer card describing call-initiation throughput and when to increase it ## When to raise CPS High-volume broadcast and auto-dial campaigns saturate the default CPS ceiling first. Raising it removes the throttle so a run launches thousands of calls in seconds rather than minutes. The symptom of a CPS ceiling is a [campaign](/docs/platform/campaigns/list) that completes correctly but slowly - attempts trickle out at a steady rate no matter how much concurrency is free. If instead callers hit busy signals, concurrency is the limit, not CPS. ## Buying capacity | Control | What it does | | -------------------------- | ----------------------------------------------------------------------------------------------------------------- | | **Quantity** | Stepper in **blocks of 3**, minimum 3. The − and + buttons move a full block at a time. | | **Estimated monthly cost** | Recalculates as you step the quantity, before you commit to anything. | | **Bracket table** | The pricing tier applied to your selection - the bracket, the units bought, the price per unit, and the subtotal. | | **Buy CPS** | Purchases the capacity and starts a monthly subscription. | Capacity is **purchased in blocks of 3 and billed monthly**. The first month is charged on purchase, and the subscription then renews on its own cycle until you cancel it from [My Subscriptions](/docs/platform/capacity/subscriptions). The prices in the screenshot belong to one account's pricing tier. Your own rate appears in the bracket table as you change the quantity, and [Preview capacity pricing](/docs/account/channel-pricing-preview) returns the same figure over the API without charging anything. ## Buy it over the API Calculate the monthly price for a CPS quantity without creating a subscription. Create the subscription with `resource_type: "cps"` and a quantity.