To replace the portable radio sets SE-206/9 and the vehicle sets SE-407/11, a call for projects was made in the sixties. A consortium called ABZ, consisting of the RF radio sections of Autophon - Brown Boveri and Zellweger startet the developing project „Peter“ in 1966. Because the expectations were high and they were changed when new technical possibilities were available, it was stopped and relaunched in 1972. Even then, it took many years until the st was ready for production.
In the meantine, the american armoured vehicle M113 had been acquired, together with the american radio sets VRC-12 which were already installed in the tanks. These radio sets turned out to be very versatile, the frequencies could be tuned without the need for frequency crystals. One drawback was that the communication was not encrypted, so codelists and „message blurring“ were to be used to prevent the interception of the messages by enemy forces.
For the infantry and for the armoured vehicle troops, large numbers of the VRC-12 (SE-412) and the matching manpack sets PRC-77 (SE-227) have been ordered. Until the 20th century came to an end, these sets were the backbones of tactical radio use in the Swiss Army. In the end, only for the Airforce and anti aircraft units, some 3000 units of the improved SE-225 have been ordered. The development of the set has been accomplished in 1986 and it was introduced with the troops in 1992/4.
Mobile use with NiCd accumulator (AKF-225) or Li battery (BAF-225), from vehicle battery 12/24 V (Vehicle mount EA-225), with buffer unit PE-225 interrupted mains supply could be bridged with an accumulator; as an alternative mains 220 V with mains power supply NG-225.
The SE-225 could be used with the portable antenna MA-225 (omnidirectional 1,6 m whip antenna), an omnidirectional vehicle antenna FZA-225 (1,9 m) or long distance antenna FA-225 (omnidirectional antenna on an eight segment fiberglass mast, maximum height 10,8 m).
The power amplifier LV-225 gives the possibility to select the output power between 400 uW / 0,4 W / 4 W and 40 Watt.
A remote control unit (Fernbetriebsausrüstung FBA-225) is used to remote control the set over field telephone lines from up to 3 km, there are the options for service telephone communication and for signalling radio silence and fixed frequency operation. With an RS-323 interface, data mode transmissions with up to 1200 Baudare possible.
The intercom BVA-225 with a central intercom amplifier BZ-225, control box, monitor and noise headgear LG-225 has never been introduced as the tank units had been equipped with the SE-412 and the option for an onboard intercom was not considered as necessary for the airbourne units.
The SE-225 is a frequency-modulated military radio set, which was designed for portable use (as a „man-pack“), for mobile use onboard vehicles and for operation in fixed installations.
In the frequency range 30 - 87 MHz, the frequency selection is fully automatic. Each time a connection is established (when the transmit button is pressed), the set selects an available unocupied channel from a bunch of frequencies and transmits as long as the transmit button is pressed down. So one frequency is only occupied for a short moment and shortly after, is is released to be used by other users.
The set operates in frequency modulation in the frequency range of 30 - 87 MHz. A total of 76 (19 x 4) channel bundles occupying a bandwidth of 3 MHz each can be used. In each bundle, 30 frequencies with a channel spacing of 100 kHz can be used. With the built in selective call technology, in each network, 1 to 9 participants in can be called up individually.
The front panel has a straightforward design. On the left you will find the socket for the mobile antenna and the 50 Ohm antenna connector, to the right of the antenna connectors, the frequency switch, the mode switch and the volume control and on the top right the connectors for the combines microtelephone / control unit BG-225 and the remote control unit FBG-225.
The mode switch has the positions FF (fixed frequency operation, also used for communication with older sets such as SE-125, SE-227 and SE-412), OFF, radio operation without and with call buzzer, radio silence and RE (relay operation), to activate the first and the last position, the switch must slightly be pulled out.
If the volume switch is turned to the left, the dial windows of the channel bundle address indicator are illuminated and a self-test is performed. Turned to the right, the volume can be set to four positions.
The actual transceiver needs a control unit BG-225 , a microtelephone with an integrated keyboard, for proper operation, programming the radio and entering the encryption key. The most important controls are the push-to-talk button to initiate a call and for receive / transmit switching, and the „free“ key (F) for disconnecting the call. The key with the key symbol is used for encrypted operation and the one with the triangle to activate clear / uncrypted operation.
The first four display segments indicate the channel bundle number and frequency in the fixed frequency mode. The entire frequency range of the SE-225 is divided into 19 channel bundles with a channel band width of 3 MHz. The lowest frequency is calculated from 27 + X times 3 MHz, so channel bundle 9 starts at 54 MHz.
The next digit of the display indicates channel bundle A to D (A stands for frequencies ending with 000 MHz, B for frequencies ending with x25 MHz, C for frequencies ending with x50 MHz, D for frequencies ending with x75 MHz.
The next two digits from 00 to 29 denote the 100 kHz digits in the respective 3 MHz range, for the frequency 56.425 MHz therefore 9 (range from 54 MHz), B 24 must be set.
Each network is thus assigned one channel bundle consisting of a bundle number 1-19 and the bundle group designation A-D.
In selective call operation, each set is assignes a three-digit decimal number. The first two digits stand for the group number (01 - 99) and the last for the individual subscriber number (1-9). To each SE-225, three selective call addresses can be programmed, so one set can be assigned to three different networks. In order to selctively call a station, the individual has to be callud up by its group number (01-99) and subscriber number (1-9). Additional informations such as relay operation, broadcast operation (to all subscribers in the network) can also be transmitted. In each control unit BG-225, up to ten subscriber numbers can be stored.
The SE-225 contains built-in encryption (speech scrambling), each encryption key consists of twelve digits. Four digits of the key are preset and the other 8 digits must be entered with the keypad; the key stored in memory channel 0 is automatically used as master key for all connections, unless another key is used.
In the manpack variant, the transceiver and a lithium battery or accumulator is mounted on a TR-225 carrying frame with an accessory compartment; together with the batteries, the radio has a weight of 13.0 kg.
The set is completely solid state.
When plans were made to develop a radio as successor to the manpack and mobile stations SE-206 and SE-407, three major Swiss mobile communication companies joined forces for the co-development of a new communications system according to the requirements of the Swiss armed forces, called „Project Peter“. Due to high technical expectations and the rapid development with the transition from valve to transistor and then integrated circuit technology in these years, the whole project was put on ice in 1972 and re-launched a few years later.
Nevertheless, the development of a set with automatic selection of a frequency out of a selected frequency bundle and integrated speech encryption took many years. Several technologies developed for this set were introduced in mobile telephone technology later on (automatic channel selection and encryption), but the set was not ready for production before 1986.
Until then, the infantry and the armoured vehicle corps had already become accustomed to the technically fas less advanced American devices SE-227 (AN/PRC-77) and SE-412 (AN/VRC-12) and to use of code lists. The U.S. sets were bought in a number of thousands, so that the technically advanced SE-225 was finally introduced only with the Airforce / antri aircraft units, which bought 2995 sets.
The sets with an abz label (which stands for the consortium of Autophon - Brown Boveri - Zellweger were part of a larce scale trial with the armed forces, the definitive got a nameplate of the successor company Ascom, to which the participants of consortium abz had merged in the meantime.
The components of the abz pre production series are not 100% compatible with the definitive components and their racks.
After quite a short period of time, however, the SE-225 set was already outdated, it was replaced by a new generation of radios with similar features, but digital technology fully implemented.
The SE-225 was used by the Air Force / anti aircraft units and also replaced the SE-221 in their role as water warning service radio.