Product Support
Welcome to Product Support. Enter your model number to retrieve manuals, frequently asked questions (FAQs), troubleshooting tips, and additional resources.
Need help finding your model number? Take a look here.
How To Find Your Model Number
Turn over the base of your product to locate the model number as illustrated in the image below.
5.8 GHz digital expandable phone system with color handset
I5857
Manuals & Documentation
Frequently Asked Questions
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For message recording, your telephone has a Built-in answering system, and it also supports Voicemail service offered by your telephone service provider(subscription is required, and fee may apply).
The main differences between them are:
BUILT-IN ANSWERING SYSTEM VOICEMAIL SERVICE SUPPORTED BY Telephone system Telephone service provider SUBSCRIPTION No Yes FEES No May apply ANSWER INCOMING CALLS •After 3 rings by default.
•It can be changed via handset or the telephone base menu.•Usually after 2 rings.
•It can be changed by contacting your telephone service providerSTORAGE Telephone base Server or System DISPLAY NEW MESSAGE • Handset - XX new messages
• Telephone base - XX new messages• Handset - 
and New voicemail
• Telephone base -
RETRIEVE MESSAGES • Press PLAY/STOP on the telephone base; OR
• Press MENU, and then select Play messages on the handset; OR
•Access remotely with an access code• Press 
on the dialpad, and enter an access number from your telephone service provider.Based on the above information, if you want to...
Use the built-in answering system to record your messages
Your Voicemail service can bundle in your telephone plan. As such, you would need to contact your telephone service provider to disable it.
*TIP: Can I switch back to Voicemail service if I want to?
As long as your telephone plan includes the Voicemail service, you can still re-enable it through your service provider.Use the voicemail service to record your messages
Simply turn off the Built-in answering system at any time, and you can use the Voicemail service only.Use both the Built-in answering system and the Voicemail service to record messages
By default, the Voicemail service is usually set to answer after 2 rings, while your Built-in answering system is set after 3 rings. Please check with your telephone service provider to learn how to set your voicemail settings.Suggest to set your Built-in answering system to answer calls at least 2 rings earlier than your Voicemail service. In other words, if your answering system sets to answer after 3 rings (by default), then you need to set the Voicemail service to answer after 5 rings.
What happened is that if you on a call or the answering system is already recording, and you receive ANOTHER incoming call, then the third caller is able to leave a Voicemail message.
On the other hand, if you are not on a call nor the answering system is recording, the incoming caller can leave a message directly to the Built-in Answering system.
Why won’t the battery(s) in my telephone handset hold a charge?
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Tip 1 of 4
Confirm proper installation of the telephone base power supply and handset battery. You should only use the VTech power supply provided with your telephone. Make sure the power supply is not connected to an electrical outlet that is controlled by a wall switch. Confirm that the electrical outlet that the telephone is plugged into is working. -
Tip 2 of 4
Make sure you are using the batteries supplied with your phone. DO NOT USE NON-RECHARGEABLE BATTERIES!.
If you are replacing the batteries and need assistance, refer to our VTech Battery Finder. If batteries for your model are unavailable, you can search the internet using the key words cordless phone batteries for an on-line supplier. If you prefer to purchase locally, you can look for replacement batteries at your area consumer electronics retailers. It is recommended that you take your present battery with you to insure that the replacements are the correct size and have the correct specifications. -
Tip 3 of 4
When placing the handset in the charging base, confirm that the charge contacts on the handset and base are making a good connection. The CHARGING light on the telephone base will be on when the handset is charging.
You should allow 10-12 hours to fully charge the handset battery. For optimum daily performance, return the handset to its telephone base when not in use. -
Tip 4 of 4
You may need to replace the handset batteries, especially if they have been in service for more than one year. To find replacements, refer to our VTech Battery Finder. If batteries for your model are unavailable, you can search the internet using the key words cordless phone batteries for an on-line supplier. If you prefer to purchase locally, you can look for replacement batteries at your area consumer electronics retailers. It is recommended that you take your present battery with you to insure the replacements are the correct size and have the correct specifications.
Why do calls fade/cut in and out when I’m using this phone?
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Tip 1 of 8
If you subscribe to DSL service for this telephone line, DSL filters must be plugged into EVERY phone jack that has a phone. The DSL signal can cause static/noise, squealing (similar to fax tones), caller ID disruption and other issues on your line. DSL filters block the high frequency DSL signals from being transmitted to the telephone. If you are not using the DSL filters provided by the telephone company, this will cause static/noise and possibly caller id issues on your phones.
In most cases, we recommend you connect the plug end of the DSL filter into the telephone jack, then connect a telephone cord between the filter and your phone.
Please contact your service provider to obtain DSL filters and installation information. -
Tip 2 of 8
Move the handset closer to the base. The operating range may vary with environmental conditions and time of use. There may be places within your environment that a cordless phone will not work well. If the problem only occurs in certain areas of your environment, you can conclude that there is nothing wrong with the phone. Consider trying a phone that operates on a different wireless frequency. -
Tip 3 of 8
Other electronic products (i.e., 802.11 wireless networking products, radios, radio towers, pager towers, cell phones, intercoms, room monitors, televisions, personal computers, kitchen appliances and other cordless phones) can cause interference with your cordless phone. Try installing your phone as far away as possible from these types of electronic devices. -
Tip 4 of 8
To get better reception, try moving the telephone base to higher location. Relocate telephone base near a window if using telephone outside. -
Tip 5 of 8
There may be places within your environment that a cordless phone will not work well. If the problem only occurs in certain areas of your environment, there is nothing wrong with the phone. This is normal radio operation. -
Tip 6 of 8
You may have a defective telephone cord. Try replacing cord between the jack and telephone base. -
Tip 7 of 8
Excessive background noise will cause a speakerphone to fade in and out. Try controlling the background noise by turning off any audio devices near the speakerphone. Also, try to avoid interrupting the person at the other end of the conversation while they are speaking. If background noise cannot be controlled, you should terminate speakerphone operation and return to normal handset mode. -
Tip 8 of 8
If you have connected this telephone to a phone jack that has not been used before, or that has not been used in sometime, there may be problems with this jack that you are not aware of. Use a telephone jack that you know is in proper working order.
Why won’t the CHARGING light turn on when I place the handset in the base?
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Tip 1 of 9
Confirm proper installation of the handset batteries. If a battery is missing or installed wrong, you will see this error message: WARNING CHECK BATTERY! The proper installation procedure for the batteries is as follows:
Step 1: Place the batteries in the compartment. Be careful to ensure that each cell is in the correct orientation.
Step 2: Replace cover by sliding it upwards until it clicks into place.
Step 3: Be sure to charge the handset for a minimum of 10-12 hours before using your phone. -
Tip 2 of 9
When placing the handset in the charging base, confirm that the charge contacts on the handset and base are making a good connection. The CHARGING light on the telephone base will be on when the handset is charging.
You should allow 10-12 hours to fully charge the handset battery. For optimum daily performance, return the handset to its telephone base when not in use. -
Tip 3 of 9
Make sure you are using the batteries supplied with your phone. DO NOT USE NON-RECHARGEABLE BATTERIES!.
If you are replacing the batteries and need assistance, refer to our VTech Battery Finder. If batteries for your model are unavailable, you can search the internet using the key words cordless phone batteries for an on-line supplier. If you prefer to purchase locally, you can look for replacement batteries at your area consumer electronics retailers. It is recommended that you take your present battery with you to insure that the replacements are the correct size and have the correct specifications. -
Tip 4 of 9
Confirm proper installation of the telephone base power supply and handset battery. You should only use the VTech power supply provided with your telephone. Make sure the power supply is not connected to an electrical outlet that is controlled by a wall switch. Confirm that the electrical outlet that the telephone is plugged into is working. -
Tip 5 of 9
Please make sure that the cords (power and telephone line) are plugged into the channels on the bottom of the base. If the cords are not properly installed, the base will not sit level and the phone may not charge properly. -
Tip 6 of 9
Dirty charge contacts on the telephone base and handset could prevent the batteries from charging. Clean the handset and base charge contacts using a pencil eraser or a cloth to eliminate deposit accumulation. -
Tip 7 of 9
Make sure that the battery cover is properly secured on the handset. If the battery cover is not correctly installed, it may prevent the handset from charging. -
Tip 8 of 9
If the handset is not responding normally, you may need to reset your telephone system. Complete the following steps to reset the telephone system:
Step 1: Disconnect the power to the telephone base.
Step 2: Disconnect the handset battery.
Step 3: Wait a few minutes and then reconnect the power to the telephone base.
Step 4: Reconnect the handset battery
Step 5: Wait about one minute for the handset to re-establish a link with the telephone base and then test the phone again. -
Tip 9 of 9
You may need to replace the handset batteries, especially if they have been in service for more than one year. To find replacements, refer to our VTech Battery Finder. If batteries for your model are unavailable, you can search the internet using the key words cordless phone batteries for an on-line supplier. If you prefer to purchase locally, you can look for replacement batteries at your area consumer electronics retailers. It is recommended that you take your present battery with you to insure the replacements are the correct size and have the correct specifications.
My telephone handset appears to be dead. What should I do?
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Tip 1 of 13
If your handset responds in any way (beeps, displays a message on the screen, etc.) then it is not dead. Please review the Frequently Asked Questions list to check for a more specific symptom to your problem.
A common cause for dead handset symptoms is a dead battery. We recommend that you initially charge the handset battery for 12 hours. If the handset does not hold a charge or seems dead, we suggest the following:
• Please verify that the handset battery(s) is securely plugged into the back of the handset.
• Check that there is power to the base and cradle. If there is power and the handset is cradled face up, the CHARGING light on the base will be on.
• Place the handset in the cradle and charge it overnight.
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Tip 2 of 13
Make sure you are using the batteries supplied with your phone. DO NOT USE NON-RECHARGEABLE BATTERIES!.
If you are replacing the batteries and need assistance, refer to our VTech Battery Finder. If batteries for your model are unavailable, you can search the internet using the key words cordless phone batteries for an on-line supplier. If you prefer to purchase locally, you can look for replacement batteries at your area consumer electronics retailers. It is recommended that you take your present battery with you to insure that the replacements are the correct size and have the correct specifications. -
Tip 3 of 13
Confirm proper installation of the telephone base power supply and handset battery. You should only use the VTech power supply provided with your telephone. Make sure the power supply is not connected to an electrical outlet that is controlled by a wall switch. Confirm that the electrical outlet that the telephone is plugged into is working. -
Tip 4 of 13
Please make sure that the cords (power and telephone line) are plugged into the channels on the bottom of the base. If the cords are not properly installed, the base will not sit level and the phone may not charge properly. -
Tip 5 of 13
Dirty charge contacts on the telephone base and handset could prevent the batteries from charging. Clean the handset and base charge contacts using a pencil eraser or a cloth to eliminate deposit accumulation. -
Tip 6 of 13
Make sure that the battery cover is properly secured on the handset. If the battery cover is not correctly installed, it may prevent the handset from charging. -
Tip 7 of 13
When placing the handset in the charging base, confirm that the charge contacts on the handset and base are making a good connection. The CHARGING light on the telephone base will be on when the handset is charging.
You should allow 10-12 hours to fully charge the handset battery. For optimum daily performance, return the handset to its telephone base when not in use. -
Tip 8 of 13
Make sure your handset is registered to the base unit. Refer to the Registration procedure in the User’s Manual. -
Tip 9 of 13
Other electronic products (i.e., 802.11 wireless networking products, radios, radio towers, pager towers, cell phones, intercoms, room monitors, televisions, personal computers, kitchen appliances and other cordless phones) can cause interference with your cordless phone. Try installing your phone as far away as possible from these types of electronic devices. -
Tip 10 of 13
To get better reception, try moving the telephone base to higher location. Relocate telephone base near a window if using telephone outside. -
Tip 11 of 13
Recradle the handset for 15 seconds, then lift the handset and press ON. -
Tip 12 of 13
If the handset is not responding normally, you may need to reset your telephone system. Complete the following steps to reset the telephone system:
Step 1: Disconnect the power to the telephone base.
Step 2: Disconnect the handset battery.
Step 3: Wait a few minutes and then reconnect the power to the telephone base.
Step 4: Reconnect the handset battery
Step 5: Wait about one minute for the handset to re-establish a link with the telephone base and then test the phone again. -
Tip 13 of 13
You may need to replace the handset batteries, especially if they have been in service for more than one year. To find replacements, refer to our VTech Battery Finder. If batteries for your model are unavailable, you can search the internet using the key words cordless phone batteries for an on-line supplier. If you prefer to purchase locally, you can look for replacement batteries at your area consumer electronics retailers. It is recommended that you take your present battery with you to insure the replacements are the correct size and have the correct specifications.
Why does my handset display "LINE IN USE"?
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Tip 1 of 2
When a system handset or base speakerphone (where applicable) is on a call, the idle system handsets and base will display LINE IN USE. -
Tip 2 of 2
The unit will display EXT. IN USE when another phone on the line is in use. The phone will display this because the unit has sensed a change in the line voltage when a phone is turned on.
If there is not another phone off hook when it displays this message, there may be temporary fluctuation in the line voltage. There is nothing malfunctioning with the unit, but you may need to contact your telephone company if this issue persists.
Why is WARNING CHECK BATTERY! shown on the handset display when I put it in the base?
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Tip 1 of 3
You may need to replace the handset batteries, especially if they have been in service for more than one year. To find replacements, refer to our VTech Battery Finder. If batteries for your model are unavailable, you can search the internet using the key words cordless phone batteries for an on-line supplier. If you prefer to purchase locally, you can look for replacement batteries at your area consumer electronics retailers. It is recommended that you take your present battery with you to insure the replacements are the correct size and have the correct specifications. -
Tip 2 of 3
Confirm proper installation of the handset batteries. If a battery is missing or installed wrong, you will see this error message: WARNING CHECK BATTERY! The proper installation procedure for the batteries is as follows:
Step 1: Place the batteries in the compartment. Be careful to ensure that each cell is in the correct orientation.
Step 2: Replace cover by sliding it upwards until it clicks into place.
Step 3: Be sure to charge the handset for a minimum of 10-12 hours before using your phone. -
Tip 3 of 3
Make sure you are using the batteries supplied with your phone. DO NOT USE NON-RECHARGEABLE BATTERIES!.
If you are replacing the batteries and need assistance, refer to our VTech Battery Finder. If batteries for your model are unavailable, you can search the internet using the key words cordless phone batteries for an on-line supplier. If you prefer to purchase locally, you can look for replacement batteries at your area consumer electronics retailers. It is recommended that you take your present battery with you to insure that the replacements are the correct size and have the correct specifications.
How do I register a new accessory handset to the base?
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To register a handset to the base, follow these steps:
Step 1: Locate the 15-digit Base ID number by pressing, at the base: MENU, then press ▼ until DISPLAY BASE-ID is highlighted, then press OK.
Step 2: Carefully enter this number using the handset dialpad. If you make a mistake, press ‹ to backspace. When finished, press OK.
In a few moments, the handset will be assigned a number (1-8). This will be the lowest available number in the sequence not previously assigned to another system handset.
Step 3: Repeat the procedure for any other unregistered system handsets
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First, deregister all handsets:
Step 1: At the base, press MENU, scroll to BASE SETTINGS, then press OK.
Step 2: Using the base dialpad, enter * * 3 3 5 7 8 2
Step 3: Re-register each system handset:
At the base, press MENU, scroll to DISPLAY BASE-ID, then press OK. The 15-digit base ID number will be displayed.
Step 4: Using the handset dialpad, enter the base ID number. Repeat the registration procedure for each system handset. Each handset is assigned a number in the order of registration.
Some or all of the keys on my handset are not functioning. What should I do?
- Sticking keys can trigger dialing errors. Try cleaning the keypad and around the buttons with a soft, slightly damp cloth.
Why am I not receiving caller ID on my phone?
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Caller ID and Call Waiting ID are subscription services, available from most local telephone service providers. You must subscribe to these services in order for the features to work on your phone. Contact your local telephone service provider for more information.
In addition, your caller must be calling from an area that supports caller ID.
Both you and your caller’s telephone service provider must use compatible caller ID systems.
If you subscribe to DSL service for this telephone line, DSL filters must be plugged into EVERY phone jack that has a phone. The DSL signal can cause caller ID disruption, static, noise and other issues on your line. DSL filters block the high frequency DSL signals from being transmitted to the telephone. If you are not using the DSL filters provided by the telephone company, this will cause static/noise and possibly caller id issues on your phones.
In most cases, we recommend you connect the plug end of the DSL filter into the telephone jack, then connect a telephone cord between the filter and your phone.
Please contact your service provider to obtain DSL filters and installation information.
Caller ID and Call Waiting ID may not be available for every call. Common reasons are incompatibilities between your and your caller’s service, transmission errors and answering calls before the ID data is received.
How can I improve the sound quality on my cordless phone?
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If your handset has a CHANNEL (or CHAN) button, press it in order to improve the sound quality. You may need to press the CHANNEL button more than once.
The handset may be out of range. Try moving closer to the base. The handset(s) and base can only communicate over a certain distance which can vary with their placement, the weather and the operating environment of your home/office.
If you subscribe to DSL service for this telephone line, DSL filters must be plugged into EVERY phone jack that has a phone. The DSL signal can cause static/noise, squealing (similar to fax tones), caller ID disruption and other issues on your line. DSL filters block the high frequency DSL signals from being transmitted to the telephone. If you are not using the DSL filters provided by the telephone company, this will cause static/noise and possibly caller id issues on your phones.
In most cases, we recommend you connect the plug end of the DSL filter into the telephone jack, then connect a telephone cord between the filter and your phone.
Please contact your service provider to obtain DSL filters and installation information.
A low battery pack may affect the sound quality. You may need to charge the handset. Also, try repositioning the handset against your ear until the sound quality improves.
Electronic products (i.e., 802.11 wireless networks, radios, radio and pager towers, cell phones, intercoms, room monitors, televisions, personal computers, kitchen appliances and other cordless phones) can cause interference with your cordless phone. Try installing your phone as far away as possible from these types of electronic devices.
Appliances or other cordless phones plugged into the same circuit as the telephone base can cause interference. Try moving the appliances or telephone base to another outlet.
Microwave ovens may operate on the same frequency as your telephone. You may experience static on your telephone while the microwave oven is operating. Do not install your cordless telephone in the same outlet or near the microwave oven.
Disconnect the telephone base from the modular jack and plug in a corded telephone. If calls are still not clear, the problem is probably in the wiring or local service. Contact your local service company (charges may apply).
If your phone shares a power outlet with a modem, or if it is plugged into a shared surged protector, try plugging in the phone (or modem/surge protector) at a different location. If this solves the problem, relocate your phone and modem farther apart from each other, or use separate surge protectors.
The layout of your home or office may be limiting the operating range. Try moving the base to another location, preferably a higher location for better reception. If your telephone base has an adjustable antenna, ensure it is pointing up.
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Tip 1 of 7
Move the handset closer to the base. The operating range may vary with environmental conditions and time of use. There may be places within your environment that a cordless phone will not work well. If the problem only occurs in certain areas of your environment, you can conclude that there is nothing wrong with the phone. Consider trying a phone that operates on a different wireless frequency. -
Tip 2 of 7
Make sure that the power cord is securely plugged into the base and electrical outlet. Make sure the electrical outlet is not controlled by a wall switch. -
Tip 3 of 7
Recradle the handset for 15 seconds, then lift the handset and press ON. -
Tip 4 of 7
Other electronic products (i.e., 802.11 wireless networking products, radios, radio towers, pager towers, cell phones, intercoms, room monitors, televisions, personal computers, kitchen appliances and other cordless phones) can cause interference with your cordless phone. Try installing your phone as far away as possible from these types of electronic devices. -
Tip 5 of 7
To get better reception, try moving the telephone base to higher location. Relocate telephone base near a window if using telephone outside. -
Tip 6 of 7
If the handset is not responding normally, you may need to reset your telephone system. Complete the following steps to reset the telephone system:
Step 1: Disconnect the power to the telephone base.
Step 2: Disconnect the handset battery.
Step 3: Wait a few minutes and then reconnect the power to the telephone base.
Step 4: Reconnect the handset battery
Step 5: Wait about one minute for the handset to re-establish a link with the telephone base and then test the phone again. -
Tip 7 of 7
Make sure your handset is registered to the base unit. Refer to the Registration procedure in the User’s Manual.
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Despite your VoIP box shows full signal strength, there could still be no dial tone/ display Line in Use/ etc. This may due to the abnormality of signal and voltage levels. Follow this short video to reset your VoIP box and its connected devices.
(For non-IS8151 series - all other models) https://www.youtube.com/watch?v=mXbXl4froUc&t=25s
(For IS8151-X series) https://www.youtube.com/watch?v=rJ9PNkwBzfE&t=3s
[Background]
• VoIP box connected via SIM/ LAN connection.
• Some VoIP boxes have displays and some not. While displays show steady ON and ready, you might still experience with no dial tone sound/ display Line in Use.[To Reset]
• Some Power off button does not fully power off the unit. It only put the VoIP box in standby mode. To truly power off, unplug the power adapter of your VoIP box.
• Disconnect all devices from the box. After a moment, reconnect your power adapter, and then press power button to turn ON.
• Wait until the VoIP box is steady ON and ready.
• Connect your telephone cable from your Telephone base to your VoIP box.REMINDER!!!
• Make sure you didn't connect the telephone cable from the Telephone wall outlet to VoIP box telephone port!!! Doing so will not damage the device, but it will affect the call function and becomes unusable. This is why you experience no dial tone, Line in Use with busy tone, etc.
• During power outage, your landline phone will not be available since it requires external electric power despite your VoIP box has a backup battery.If this situation persists, contact your VoIP / VoIP box service provider for further support.