# *#43# on iPhone: Check Call Waiting URL: https://byshahid.com/blog/check-call-waiting-star-hash-43-iphone/ App: Secret Codes: IMEI & Carrier (https://apps.apple.com/us/app/secret-codes-imei-carrier/id6807154322) Author: Muhammad Shahid Updated: 2026-11-04 > *#43#: See whether a second incoming call will interrupt you. Interrogates the call waiting supplementary service. The network reports whether it is active for voice calls. Call waiting interacts with busy forwarding — if both are on, the network offers you the waiting call first and only forwards it when you decline. - **Code:** *#43# - **What it does:** See whether a second incoming call will interrupt you. - **Published for:** AT&T and T-Mobile - **Type:** GSM networks See whether a second incoming call will interrupt you. This page explains what `*#43#` does, how to use it on an iPhone and which carriers it applies to. I build **Secret Codes: IMEI & Carrier**, a free iPhone app with 317 checked codes and guides, including this one. If you would rather tap than memorise, [get Secret Codes on the App Store](https://apps.apple.com/us/app/secret-codes-imei-carrier/id6807154322). ## What does *#43# do? Interrogates the call waiting supplementary service. The network reports whether it is active for voice calls. Call waiting interacts with busy forwarding — if both are on, the network offers you the waiting call first and only forwards it when you decline. ## How do I use *#43#? - Open the Phone app and tap Keypad. - Type *#43# exactly as written. - Press the green Call button and wait for the result. ## Which carriers does this apply to? | Published for | AT&T and T-Mobile | | Type | GSM networks | | Good to know | GSM networks only. iOS also exposes call waiting as a switch under Settings › Phone. | _Screenshot: The Secret Codes detail screen shows the steps, the carriers and an Open in Phone button._ ## Related network and signal - [*#5005*7672#: Check Your SMS Centre Number](/blog/check-your-sms-centre-number-star-hash-5005-star-7672-iphone/) - [*43#: Turn On Call Waiting](/blog/turn-on-call-waiting-star-43-iphone/) - [*3001#12345#*: Field Test Mode](/blog/iphone-field-test-mode/) - [#43#: Turn Off Call Waiting](/blog/turn-off-call-waiting-hash-43-iphone/) - [*#33#: Check Call Barring](/blog/check-call-barring-star-hash-33-iphone/) - [Choose Your Network Manually](/blog/choose-your-network-manually-iphone/) See all [network and signal](/blog/iphone-codes/network/) or [every category of iPhone codes](/blog/iphone-codes/). ## How Secret Codes helps Secret Codes keeps this and every other entry a search away. Pick your carrier once and each entry says whether it is published for your line. You can save favourites, add a private note, and record whether a code worked on your line. **Secret Codes: IMEI & Carrier** is free on the App Store: https://apps.apple.com/us/app/secret-codes-imei-carrier/id6807154322 ## FAQ ### What does *#43# do on iPhone? See whether a second incoming call will interrupt you. Interrogates the call waiting supplementary service. The network reports whether it is active for voice calls. ### What else should I know about *#43#? Call waiting interacts with busy forwarding — if both are on, the network offers you the waiting call first and only forwards it when you decline. ### What are the steps for *#43#? 1. Open the Phone app and tap Keypad. 2. Type *#43# exactly as written. 3. Press the green Call button and wait for the result. ### Where do I use *#43#? On the keypad of the Phone app. ### Do I need to press Call after typing *#43#? Yes. Type it on the Phone keypad, then press the green Call button. ### Is *#43# a hidden or secret code? No. It is a standard GSM code, handled by the network rather than by a hidden menu on the iPhone. ### Which carriers does *#43# work on? It is published for AT&T and T-Mobile. GSM networks only. iOS also exposes call waiting as a switch under Settings › Phone. ### Does *#43# work on Android phones too? GSM codes are a network standard, so they generally behave the same on any phone on a network that supports them. ### Will *#43# work outside the US? It depends on the network you are on. GSM codes are a standard, but each network decides which it supports. ### What if *#43# does not work on my iPhone? Check that it applies to your carrier first, because carriers decide which services they offer and can change them. If it should apply to your line, contact your carrier. ### What is related to *#43#? *#5005*7672#: Check Your SMS Centre Number. Read back the message centre your texts route through. ### What else is in this category? *43#: Turn On Call Waiting. Allow a second call to interrupt an active one. ## Sources - [3GPP TS 22.030: Man-Machine Interface of the phone](https://www.3gpp.org/dynareport/22030.htm) - [Apple Support: iPhone User Guide](https://support.apple.com/guide/iphone/welcome/ios)