Frequently Asked Questions

Cellular/Wireless: Line Emulation Devices

The question comes in many forms:

  • Is there a cellular interface for the RFC-1/B?
  • My site has no landline/telephone service, what are my options?
  • Can the RFC-1/B be used with (insert device/service name here)?
  • The bag-phone no longer works, what replacement devices are available?

The short answer is that the RFC-1/B is designed to be connected to an ordinary (POTS) telephone line. If it is connected to a device that emulates a telephone line reasonably well, it should function normally. Reality, of course, can be different.

While most of these devices work as advertised, they are typically designed for voice traffic in an office environment. There may be issues getting clean usable signal with broadcast transmitter(s) in close proximity.

Sine Systems does not manufacture or sell the devices described on this page. The manufacturers of these devices may change the specifications without notice. Sine Systems makes no claim about the suitability of these devices with the RFC-1/B.

This page summarizes information that we have collected about the devices that are available. It is based on data provided by customers and the device manufacturers. The information is believed to be accurate. Wireless service varies with carrier and location. Your results may vary.

Docking Stations

These devices emulate a telephone line and they use an off-the-shelf cell phone to provide the wireless link. They are designed for use in home office environments.

Depending on the site, the cell phone may require an external antenna. This may be an issue with most small handsets. Wireless products change rapidly so it is nearly impossible to recommend a specific model.

Phone Labs Dock-n-Talk

The Dock-n-Talk is described as a "universal cell phone docking station". It supports a large number of handset models–mostly over Bluetooth®. This is not necessarily bad but it is something to consider in an RF heavy environment. At last check some handsets were supported with model-specific cable adapters.

We have successfully tested the Dock-n-Talk with the RFC-1/B on a local carrier with both incoming and outgoing calls. Our test system used a cabled handset. This device supports so many cell phones that we cannot possibly perform exhaustive testing or guarantee performance with any given handset/carrier combination.

Feedback from users of the Dock-n-Talk is generally positive. Be aware that on some phone models the handset volume also controls the volume of the audio through the Dock-n-Talk to the wired device. It may be necessary to adjust the handset volume up or down to get DTMF tones to the RFC-1/B at an appropriate level.

Fixed Location Cellular Phones

An alternative to using a mobile cell phone with an RJ-11 adapter is to use a phone designed specifically for fixed locations. These devices combine the wireless radio and line emulation hardware into one device.

Fixed location devices tend to cost more than docking stations but they are typically more flexible and more robust then their low-cost counterparts. For instance, most fixed-location devices easily support an external antenna.

Telular Wireless Terminals

Telular Corporation manufacturers fixed location wireless terminals. They have devices for both GSM and CDMA wireless service. Feedback from the field indicates that GSM devices work better than CDMA devices with the RFC-1/B. Telular products are available from several online resellers.

We have successfully tested the RFC-1/B with a Telular SX5T on a local GSM-based carrier with both incoming and outgoing calls. We cannot perform exhaustive testing or guarantee performance with any given device/carrier combination.

Feedback from the field is generally positive with Telular devices. They tend to be better than the Dock-n-Talk at decoding the DTMF generated by the RFC-1/B for outgoing calls.

The most common issue noted by users is that some locations do not pass DTMF tones at a strong enough level to work without modifying the RFC-1/B. There is an Engineering Bulletin in the Tech Support area of our website that describes the modification.

Radiotelephones and Wireless Extenders

This class of devices use a full duplex radio circuit to extend a POTS telephone line over a radio link. Two small transceivers are used. One is connected to the telephone line, the other end has an RJ-11 jack that emulates a telephone line.

Radiotelephones have a range of roughly 1 to 20 miles depending on terrain. Typically these systems must be licensed. Channels are usually available in the areas where radiotelephones are most often needed.

Radiotelephone systems can be expensive initially but there is no recurring cost for service once the system installed.

Ritron TeleNexus

Ritron manufactures radiotelephones and many related devices. The TeleNexus system consists of an RTLT-1 Telephone Line Terminator and an RTSU-1 Subscriber Unit. Each end of the TeleNexus system uses standard RJ11 telephone jacks.

A notable feature of the Ritron system is that it is compatible with both Touch-Tone and rotary dialing. Early RFC-1/B units were only capable of pulse dialing and due to the nature of the internal tone generator pulse dialing is still the default setting.

We have not tested the RFC-1/B with any radiotelephone devices.

Voice Over IP (VOIP) Solutions

Transmitter sites increasingly have access to broadband IP networks so voice over IP devices can potentially service products like the RFC-1/B. We are investigating available VOIP solutions and will publish details as soon as they are available.

If you have experience using the the RFC-1/B with a VOIP solution and would like to share your experience please send email to our tech support address.


We have received one review from the field that indicates that the RFC-1/B works with Vonage. We are interested in more feedback from users with Vonage. We would also like a loaner system to test in-house.

Ooma Hub

The Ooma Hub does not work with the RFC-1/B because it cannot pass inbound DTMF tones. This crippling of the device is apparently due to "a limitation with a proprietary hardware component/driver". This seems like a short-sighted design choice and it is disappointing. We were excited about a service with no monthly fee.

Ooma Telo

This device reportedly does not use the "proprietary device" that limits the Ooma Hub so we are told that the Telo will support passing DTMF tones with a firmware update to the device to be released "soon". When we hear that the firmware update is release we will test the device. We would like a loaner system to test in-house.


magicJack is a USB based device that requires a computer to work. This is not a likely solution for the typical transmitter site.

Dedicated Connection

The RFC-1 may be operated through a non-dial-up communications link such as a dedicated line, a two way radio, a pager, an STL/SCA link, etc. This additional control method may be used in place of a dial-up line or in addition to a dial-up line.

Dedicated Control Port

The Dedicated Control Port is a secondary function through the RJ-11 jack labeled "Phone" on the RFC-1/B. When this feature is activated, the RFC-1/B will be active on the local "Phone" port whenever it is not connected on a telephone call.

The communications link must isolate the RFC-1/B two-wire interface and block the 12 volts that normally powers the local phone. The device at the other end of the link must be able to generate DTMF tones to control the RFC-1/B and reproduce the audible responses from the RFC-1/B.