Timer 555 Calculator Pro vs Questar Installer
Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.
Timer 555 Calculator Pro
Calculate parameters for monostable and astable circuits. Find component combinations for desired pulse width or frequency. Share circuit files via iCloud Drive or AirDrop.
- Calculate monostable pulse width
- Calculate astable frequency
- Find component combinations
- Adjust component tolerance
- Unlimited combinations (Pro)
- Share circuit files
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This app is used to calculate monostable and astable circuit. Features * Calculate pulse width of monostable circuit * Calculate frequency of astable circuit * Find out combination of components making a desire pulse width in monostable circuit * Find out combination of components making a desire frequency in astable circuit * Share file to iCloud Drive (For iOS8 or later) * Share file via AirDrop Additional Features in the Professional Edition * Unlimited number of combinations * Allow to change tolerance * No ads
Questar Installer
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Questar Installer App is the official mobile application designed for easy, fast, and reliable installation of Questar telematics devices in vehicles. The app enables validation of cellular communication, ignition, GPS, and CAN connections, and supports adding installer comments, selecting accessories, attaching photo documentation of the installation, and navigating to the vehicle by VIN or license plate (some features may not be available in earlier versions). With seamless integration into Questar’s cloud services, the installation process becomes transparent, automated, and fully ready for large-scale deployment by partners and customers worldwide.
Screenshots
Verdict
The clearest difference is price: Questar Installer at Free against Timer 555 Calculator Pro's $0.99. On update cadence, ads, in-app purchases and device support there is nothing between them.
Scored on Price · Rating · Positive reviews · Number of ratings · Update frequency · Ads · In-app purchases · Monetization · Best chart rank · Devices · Requires iOS
Questar Installer is free to download; Timer 555 Calculator Pro costs $0.99 up front. Neither carries in-app purchases, so what you see is what you pay.
Timer 555 Calculator Pro ships an update every 3 months, Questar Installer every 4 months. The most recent releases landed on October 21, 2026 and October 7, 2026 respectively.
| Parameter | Timer 555 Calculator Pro | Questar Installer |
|---|---|---|
| Price | $0.99 | Free — better |
| Rating | 4.7 (3 ratings) — better | — |
| Positive reviews | 100.0% of reviews | — |
| Number of ratings | 3 — better | — |
| Update frequency | Every 3 months — better | Every 4 months |
| Ads | No | No |
| In-app purchases | No | No |
| Monetization | Paid | — |
| Devices | iPhone, iPad, iPod | iPhone, iPad, iPod |
| Requires iOS | 13.2 | 13.0 — better |
| Further details — not scored | ||
| Size | 3 MB | 3 MB |
| Age rating | 4+ | 17+ |
| Developer | Siu Yuen Ho | QUESTAR AUTO TECHNOLOGIES LTD |
In-app purchases
Timer 555 Calculator Pro
No in-app purchases
Questar Installer
No in-app purchases
Questions
Is Timer 555 Calculator Pro free?
Is Questar Installer free?
Do Timer 555 Calculator Pro or Questar Installer have ads?
Which is updated more often, Timer 555 Calculator Pro or Questar Installer?
Other comparisons
