The Simplex Repeater Controller Principle
The Surecom SR-112 Simplex Repeater Controller is a device that allows you to setup a “field” or “emergency” simplex repeater. In other words it is -and as we call it locally- a Parrot. It records and replays what it hears from the radio it is connected to.
So what the user has to do, is define the simplex repeater frequency, set it on the radio and connect the radio to a Simplex Repeater Controller by a purpose made/bought cable. The device will start repeating what the user will speak on the radio.
It is a dead simple, easy and economical way to set up a repeater and cover dead ground, but it does have its shortcoming. While simple technically, it is a bit complicated operationally. It requires all involved parties to expect a repetition of what they are hearing.
Let’s assume that a Simplex repeater is placed on the top of a ridge to cover its two sides. The caller will input the message on the repeater and another user on the other side will hear the repetition. but what if there is a third user on this side of the ridge, within range of the caller? It will hear the message twice! And if not advised Not to, he will probably try to respond on the call, disturbing the repetition….
The SR-112 offers some basic functions in addition to working a “Parrot”. It allows the replay of the last message, a replay of three pre-recorded messages, a remote password activation/deactivation all achieved by punching DTMF tones on your radio.
It also offers voltage, DTMF tone, audio level and battery display, not remotely but by the combination of LED colors.
For further features and specs see here
The contents of the package as it came from the eBay seller. USB wall wart, USB to DC connector cable, Kenwood type cable adapter.
The device is powered by an internal 14500 lithium battery which can re recharged. It also accepts a 5-24V DC input, a pretty wide range that allows you to hook up a USB powerbank (5V) a car battery or a car socket (12V). the power socket accepts a 5.5×2.1mm DC jack.
Taking advantage of the wide input voltage range here is my setup. A DIY 7.2V battery bank with a two prong cable for the SR-112 and power to the Baofeng battery adapter
Lastly, with the help of a multimeter and the Kenwood/Baofeng pinout I managed to find the pinout for the 3.5mm TRRS plug that connects on the device,
Surecom SR-112 pinout.
The SR-112 is quite a straightforward device of a good quality.. The device has an onboard battery, which is a definite plus, but I cannot attest on the life during use. Pictures show it to be a Trustfire protected 14500 battery, which is quite good considering it is of the economy range of Chinese Li-ion batteries.
The SR-112 manual leaves quite a lot to be desired. It does not guide the user through the setting up of the repeaters, it is mostly list of the LED audio and power readings and a list of the DTMF codes that are used for the device functions and just a few commands.
Nevertheless it still remains a useful and quite flexible device,
Suggested Videos for Further Study
Update July the 22th:
Just a few days after posting this I stumbled on another presentation video. it describes the operation better than any, and reports on a serious operating issue. Unfortunately -and for the time being- I cannot find the time to explore it myself.